IAFTC Newsletter. Volume 1. Issue 1. November 18, 2025.

Joshua Ott¹

¹Caselock, Inc., P.O. Box 285, Lebanon, GA 30146

This is an open-access article under the CC BY-NC-ND license.

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Abstract

The Drug Recognition Expert (DRE) program was developed to equip law enforcement officers with the ability to identify drivers impaired by drugs other than, or in addition to, alcohol. Although implemented across the United States, the program’s scientific basis remains contested. This paper critically examines the studies that validate the DRE’s 12-step Drug Influence Evaluation (DIE). A review of key studies—including the Johns Hopkins (1984), Los Angeles Police Department (1986), Arizona (1994), and Heishman et al. (1996, 1998) studies—reveals that DRE evaluations are not validated for actual impairment, but rather for the presence of drugs as confirmed by toxicology. False positive rates ranging from 5% to over 60% raise serious concerns about the accuracy of DRE assessments, particularly given their role in criminal prosecutions. The findings indicate that without independent, performance-based validation, the DRE program lacks the foundation necessary to serve as a scientifically valid measure of impairment.

Introduction

Drug-impaired driving presents a significant challenge for law enforcement, the legal community, and public safety. In response to limitations of toxicological testing, which cannot determine behavioral impairment, the Drug Recognition Expert (DRE) program was developed to train officers to recognize impairment in drivers by utilizing the Drug Influence Evaluation (DIE). The DIE is a standardized 12-step protocol intended to determine whether the suspect is impaired, if so, whether the cause is medical or drug-related, and if drug-related, which category or categories of drugs are the likely cause of the impairment. However, the program’s validation studies have not established that the DIE can accurately determine impairment as defined by being “less safe” to operate a vehicle. This paper critically examines the DRE program’s foundation, methods, and validation studies, arguing that the DIE lacks scientific validation for its stated purpose and carries an unacceptable rate of false positives.

Overview of the DRE Program

A Drug Recognition Expert (DRE) is an officer who has been trained to identify people who are impaired by drugs other than or in addition to alcohol. They are trained to use a standardized, systematic 12-step Drug Influence Evaluation (DIE) to determine three things.

1. Is the subject impaired?

2. Is the impairment due to medical issues or drugs?

3. If it is drugs, what category/categories of drugs is/are most likely causing the impairment? (1)

The 12-step DIE contains the following: breath test, interview of the arresting officer, preliminary examination, eye examinations, divided attention tests, vital signs (pulse is checked three separate times), pupil size and reaction to light, muscle tone, check for injection sites, subject’s statements, opinion of the evaluator, and toxicological analysis. 

To become certified, a DRE student must have a 75% toxicological corroboration rate. This means that if a DRE opines that one category of drugs is causing the impairment, that category must be confirmed by toxicology. If the DRE opines that two categories are causing the impairment, at least one must be confirmed by toxicology. If they opine that three categories are causing the impairment, at least two must be confirmed by toxicology. In the (Shinar & Schechtman, 1998) Study(2), it stated that DREs should be encouraged to always list two drug categories. Listing two drug categories increases the likelihood of the DRE identifying the correct drug category with no downside. 

Primary Validation Issue

The main issue in the DRE program lies in its reliance on toxicological confirmation as a measure of validity. Toxicology can confirm the presence of a drug or its metabolites, but it does not indicate whether the individual was behaviorally impaired. The use of toxicology in validation studies to determine the accuracy of DRE’s fails to measure the DIE’s intended purpose: identifying drivers who are less safe to operate a vehicle. This circular validation approach, where toxicology results are used to support DRE opinions, and DRE opinions are then used to claim that positive toxicology findings indicate psychoactive drug effects, fails to provide independent validation of the DIE’s ability to identify drug impairment. 

The DRE Manual states that one of the reasons for the DIE being needed is: “chemical tests usually disclose only that the subject has used a particular drug recently. The chemical test usually does not indicate whether the drug is psychoactive at the present time. Thus, the DRE procedures are needed to establish that the subject not only has used the drug, but also that he or she is under the influence.” (2025 DRE 7-Day Participant Manual, Session 3, Page 5)

Review of Key Studies

The DRE training course teaches officers about three studies, but the primary focus is on the Johns Hopkins Laboratory Study (1984)(3) and the Los Angeles Field Validation Study (1985)(4). The Arizona Study (1994)(5) is only briefly mentioned in the manual.

Johns Hopkins Laboratory Study (1984)

The Johns Hopkins study, sponsored by the National Highway Traffic Safety Administration (NHTSA), involved 80 male volunteers aged 18–35. Only four DRE raters were involved. The false positive rate was 5%. This false positive rate is potentially misleading due to the volunteers being trained on the psychomotor tasks and subjective effect questionnaires that were used in the study ahead of time. If they did not show adequate performance, they were not accepted for participation in the study. This removed potential false positives ahead of time. Additionally, the DREs were free to inquire how the subjects felt, had they ever felt that way before, or had they ever used drugs that made them feel that way, etc. These questions possibly unblinded the DREs and may have influenced their opinions.

Los Angeles Police Department Field Study (1986)

The LAPD study involved a total of 219 suspects. Twenty-eight suspects did not provide a blood sample and were not included in the final data. There were 18 suspects who were determined not to be under the influence of drugs by the DREs during the Preliminary Exam (Step 3 of the DIE) and were released from custody. This left a total of 173 suspects. 

All 173 were believed to be under the influence of drugs by the DREs. One suspect had no drugs or alcohol detected, and 10 suspects had only alcohol detected. This means that after Step 3 of the DIE, the DRE’s accuracy increased 0%. 

Adding the 18 suspects who were determined not to be under the influence of drugs during the Preliminary Exam (Step 3) to the 11 suspects who tested negative for drugs is 29. The DREs incorrectly determined that 11 out of those 29 were drug-impaired. That is a false positive rate of 37.9%.

Even the study’s authors acknowledged that drug presence does not equate to impairment, noting, 

There is no way to determine objectively whether the suspects were actually too “impaired” to drive safely. The fact that drugs were found in a suspect's blood does not necessarily mean the suspect was too impaired to drive safely. Contrary to the case with alcohol, we do not know what quantity of a drug in blood implies impairment. Thus, this study can only determine whether a drug was present or absent from a suspect's blood when the DRE said the suspect was impaired by that drug.(p. 15). 

This study failed to validate the DIE for identifying drug impairment.

Arizona Study (1994)

The Arizona study analyzed 500 records from an established DRE program. The false positive rate was 61.7%, with 42 of 68 individuals with no drugs detected being incorrectly ruled impaired. 

Heishman et al. Laboratory Studies (1996, 1998)

These were laboratory studies that were financially supported by NHTSA. Both studies used certified DREs to conduct evaluations on volunteers. The volunteers had a history of drug use and were dosed with a drug from the category that they had a history of using. In the 1996 study, DREs incorrectly identified impairment in 40.7% of placebo-dosed cases and were only 50.6% accurate in predicting the correct drug category. 

If the cases in which the DRE concluded that ethanol was causing the impairment were excluded, the DREs were only 44.4% correct in predicting the drug category. The issue with this study is that the volunteers did not reside at the location between study sessions. This allowed them to use drugs on their own and created the possibility that they were still impaired by drugs when they showed up to the next session and received a placebo dose.

The 1998 study addressed this issue by having the volunteers reside in a closed unit of the Addiction Research Center. The DREs incorrectly identified 28.1% of placebo-dosed participants as impaired and were only 32.1% accurate in identifying the correct drug category. These findings demonstrate that DREs frequently misidentify sober individuals as being impaired and lack consistent accuracy in identifying drug categories.

The (1996) study also noted, 

Until a broad range of drugs and drug doses are tested on the DEC evaluation and independent performance tests under laboratory conditions, it is difficult to assess the validity of the DEC evaluation with respect to impairment criteria. Such validation is critically needed, however, because the current means of confirming a DRE’s prediction of impairment is the presence of parent drug or metabolite in blood or urine, which, with the exception of ethanol, provides little, if any, information concerning behavioral impairment.

In the almost 30 years since this paper was published, there have been no known attempts to validate the DIE with respect to impairment criteria.

Study	Year	False Positive Rate (%)
Johns Hopkins	1984	5
LAPD	1986	37.9
Arizona	1994	61.7
Heishman et al.	1996	40.7
Heishman et al.	1998	28.1
Shinar & Schechtman	1998	56.9

Discussion

Through decades of research, no study has validated the DIE for determining actual impairment. Instead, the DIE’s accuracy is judged using toxicological confirmation, a method that is incapable of measuring drug impairment. False positive rates ranging from 5% to over 60% demonstrate an alarming lack of accuracy in correctly identifying drug-free subjects as non-impaired. 

This is particularly alarming in a world in which multiple states have legalized recreational marijuana and many people are prescribed medications that fall into the CNS Depressant, CNS Stimulant, and Narcotic Analgesic categories of the DRE program. It is very concerning in a context where DRE opinions can significantly influence legal outcomes. The omission of critical research, such as the Heishman et al. studies, from current DRE training materials raises many concerns. Without testing the accuracy of the DIE with independent performance tests as cited in Heishman et al. (1996), the DIE cannot be considered a scientifically validated method of detecting drug impairment.

Conclusion and Recommendations

The DRE program’s reliance on toxicological corroboration instead of behavioral impairment undermines its scientific legitimacy. Given the serious legal and social implications of incorrectly identifying a sober person as impaired, the DRE program’s continued use without independent validation is not acceptable. Future research must address two foundational questions: 

1. Can DREs accurately identify drivers who are less safe to operate a vehicle due to drug impairment? 

2. Can DREs accurately discriminate sober individuals from impaired ones? 

Until such evidence exists, DRE evaluations should be handled with significant caution in the legal community.

AI Use Disclosure

The author acknowledges the use of ChatGPT to refine sentence structure, enhance clarity, and correct grammatical errors. All substantive content and conclusions are the author’s own.

Conflict of Interest

The author is a consultant and expert witness for DUI cases.

References

1. 2025 Drug Recognition Expert Manuals (Pre-School and 7-Day School Instructor and Participant Manuals)

2. Modeling the DRE Evaluation of Signs and Symptoms to Improve the Validity of Drug Impairment Diagnosis, David Shinar and Edna Schechtman (1998)

3. Identifying Types of Drug Intoxication: Laboratory Evaluation of a Subject-Examination Procedure, Bigelow, Bickel, Roache, Liebson, Nowowieski (Johns Hopkins -1985)

4. Field Evaluation of the Los Angeles Police Department Drug Detection Procedure, Compton, (LAPD -1986)

5. Drug Recognition Expert (DRE) Validation Study, Eugene V. Adler and Marcelline Burns (Arizona - 1994)

6. Laboratory Validation Study of Drug Evaluation and Classification Program, Ethanol, Cocaine, and Marijuana, Heishman SJ, Singleton EG, Crouch DJ (1996)

7. Laboratory Validation Study of Drug Evaluation and Classification Program: Alprazolam, d-Amphetamine, Codeine, and Marijuana, Stephen J. Heishman, Edward G. Singleton, Dennis J. Crouch (1998)

IAFTC Newsletter. Volume 1. Issue 1. November 17, 2025.

Aaron Olson¹; Charles Ramsay²

¹ARO Consulting LLC, PO Box 132, Hugo MN, 55038

²Ramsay Law Firm, PLLC, 2780 E Snelling Ser Dr Suite #330, Roseville, MN, 55113, USA

This is an open-access article under the CC BY-NC-ND license.

Download PDF.

Introduction

On November 13, 2025, the Iowa Court of Appeals issued its decision in State v. Withers [1]. While the panel affirmed the conviction, the dissent raised substantive concerns that are directly relevant to forensic consultants and experts across the country. 

The dissent focused on the way late-disclosed forensic evidence can undermine the reliability of the judicial process and prevent meaningful scientific review. To illustrate this broader issue, the judge cited several authoritative sources on forensic reliability, including the articles Errors in Toxicology Testing and the Need for Full Discovery [2], The Courts, the NAS, and the Future of Forensic Science [3], and Invalid Forensic Science Testimony and Wrongful Convictions [4].

The citation, Errors in Toxicology Testing and the Need for Full Discovery is noteworthy for members of the International Association of Forensic Toxicology Consultants (IAFTC) because it highlights the growing recognition within appellate courts that forensic evidence requires careful evaluation, full transparency, and adequate time for expert interpretation. 

The dissent’s reasoning aligns closely with the goals of our association: ensuring that the presentation of toxicology results and their interpretation are presented to the court in a scientifically sound, properly documented, and fully discoverable manner.

Background of the Case and the Discovery Issue

Only eight days before jury selection, the prosecution disclosed a 63-page digital forensics report and a newly identified expert witness. Defense counsel stated that he did not understand the report, did not have time to consult an expert, and could not properly evaluate the accuracy or meaning of the data.

The majority held that the late disclosure did not warrant a continuance. The dissent, however, viewed the situation as fundamentally unfair and scientifically unsound.

The Dissent’s Focus on Forensic Reliability

The dissent emphasized that forensic evidence is not self-explanatory and cannot be meaningfully challenged without adequate preparation. Late disclosures deprived the defense of time to obtain independent analysis, evaluate the methodology, and examine the underlying data.

One line from the dissent captured the core concern:

“I worry that treating an untimely expert witness disclosure like any other witness disclosure perpetuates my concern about how we treat forensic evidence in the courtroom.”

Judge Sandy’s concern reflects a key point recognized by forensic science researchers and practitioners. Digital forensics, toxicology, pattern evidence, and other analytical disciplines involve complex scientific processes that demand expert interpretation. Treating an expert report as if it were equivalent to a simple fact witness disclosure ignores the reality of forensic work and its potential for error.

Why This Matters for Forensic Toxicology Consultants

There are several reasons why IAFTC members should pay attention to this development.

1. Courts are increasingly aware of the limits of forensic science

For years, many forensic disciplines have been treated as inherently credible. But recent scholarship and national reviews of forensic science, including reports from the National Academy of Sciences and the President’s Council of Advisors on Science and Technology, have prompted some courts to engage more directly with academic research when considering the reliability of forensic practices [3–6].  For example, in Birchfield v. North Dakota, 579 U.S. 438 (2016), Justice Alito’s majority opinion explicitly cited the forensic science article by A.W. Jones, titled “Measuring Alcohol in Blood and Breath for Forensic Purposes—A Historical Review,” [7,8].

2. Discovery practices directly affect our ability to provide accurate opinions

When experts receive data late or in incomplete form, it becomes difficult or impossible to evaluate whether an analysis was conducted correctly. Interpretation of toxicology results relies on instrument calibration records, raw data files, method validation studies, chain-of-custody documentation, chromatograms, and other details that are not always included in summary reports. The dissent recognized that meaningful review requires full access to this information.

3. The citation reinforces the importance of expert education and advocacy

The fact that our article was cited shows that courts recognize the role experts play in identifying laboratory errors and helping attorneys understand forensic limitations. It also affirms the importance of continuing to educate legal professionals about laboratory processes, method limitations, and the risks associated with incomplete discovery.

Implications for the Future

Judge Sandy’s dissent in State v. Withers is part of a broader trend. Courts are showing greater interest in the scientific integrity of forensic evidence, the importance of discovery, and the role of experts in ensuring accuracy. While the majority did not adopt this view in the Withers case, the presence of a detailed, research-supported dissent signals that the conversation is evolving.

Forensic toxicology consultants, especially those who provide expert testimony, should expect increasing emphasis on:

• Complete disclosure of underlying data

• Careful documentation of analytical methods

• Transparent quality control processes

• Independent review by defense experts

• Ongoing education for attorneys and judges

These themes mirror many of the IAFTC's priorities and show the growing influence of forensic scholarship on judicial reasoning.

Closing Thoughts

It is encouraging to see appellate judges cite current forensic science research in their opinions. The inclusion of toxicology-focused scholarship reinforces our field’s relevance and highlights the need for continued improvement in laboratory transparency and discovery practices.

As forensic consultants, we play a criticalrole in advancing these discussions. If IAFTC members have encountered similar issues in their jurisdictions or have examples of discovery-related challenges in forensic cases, we encourage you to share them for future newsletter features.

AI Use Disclosure

The authors used ChatGPT to assist with the organization and formatting of this article. All content was verified and substantially written by the authors, who take full responsibility for accuracy.

Declaration of competing interest

The authors declare the following financial interests/personal relationships, which may be considered as potential competing interests: Aaron Olson serves as an expert witness in forensic toxicology cases, provides consulting services through ARO Consulting LLC, and receives compensation for expert testimony and speaking engagements. Charles Ramsay is a practicing defense attorney specializing in impaired driving cases at Ramsay Law Firm, PLLC.

References

[1]State of Iowa vs. Rickie Blaine Withers Sr. 2025.

[2]Olson A, Ramsay C. Errors in toxicology testing and the need for full discovery. Forensic Sci Int Synerg 2025;11:100629. https://doi.org/10.1016/j.fsisyn.2025.100629.

[3]Garrett BL, Neufeld PJ. Invalid Forensic Science Testimony and Wrongful Convictions. Virginia Law Review 2009;95:1.

[4]Mnookin JL. The courts, the NAS, and the future of forensic science. Brooklyn Law Review 2010;75:10.

[5]The President’s Council of Advisors on Science and Technology. Forensic Science in Criminal Courts: Ensuring Scientific Validity of Feature Comparison Methods. PCAST Working Group; 2016.

[6]National Research Council, Division on Engineering and Physical Sciences, Committee on Applied and Theoretical Statistics, Policy and Global Affairs, Committee on Science, Technology, and Law, Committee on Identifying the Needs of the Forensic Sciences Community. Strengthening forensic science in the United States: A path forward. Washington, D.C., DC: National Academies Press; 2009.

[7]Jones AW. Measuring Alcohol in Blood and Breath for Forensic Purposes - A Historical Review. Forensic Sci Rev 1996;8:13–44.

[8]Birchfield v. North Dakota. 2016.

IAFTC Newsletter. Volume 1. Issue 1. November 11, 2025.

Joshua Ott¹

¹Caselock, Inc., P.O. Box 285, Lebanon, GA 30146

This is an open-access article under the CC BY-NC-ND license.

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Abstract

The Standardized Field Sobriety Tests (SFSTs) have become the primary screening tool for impaired driving enforcement since their development in the 1970s. While widely accepted in courtrooms across the United States, the actual validation data reveal significant limitations that are often overlooked or unknown by practitioners and legal professionals. This article provides an examination of the SFST validation studies, with particular emphasis on false positive rates that raise important questions about the tests. Analysis of the San Diego study reveals false-positive rates of 37% for Horizontal Gaze Nystagmus (HGN), 52% for Walk and Turn, and 41% for One Leg Stand when administered to drivers with BAC below 0.08 g/dL. The 2007 Robustness of HGN study demonstrated even higher false positive rates when HGN was administered correctly in laboratory conditions (67%), with rates exceeding 90% when stimulus positioning deviated from standardized protocols. Recent research published in JAMA (2023) examining the field sobriety tests’ ability to identify drivers under the influence of Cannabis showed false positive rates of 56% and 37% for Walk and Turn and One Leg Stand, respectively, when administered to placebo-dosed individuals. This article examines the three-phase driving under the influence (DUI) detection process, reviews the historical development and validation of SFSTs, analyzes false positive rates across multiple studies, and provides detailed guidance on proper test administration, interpretation, and common officer errors. Understanding these limitations is essential for forensic toxicologists, expert witnesses, and legal professionals who must accurately interpret SFST results in impaired driving cases.

Introduction

Since their introduction in the late 1970s, the Standardized Field Sobriety Tests (SFSTs) have become the cornerstone of impaired driving enforcement throughout the United States [1–3]. Law enforcement officers routinely administer these tests during DUI investigations, and their results often form the basis for arrest decisions and serve as critical evidence in criminal prosecutions. The tests are presented in courtrooms as scientifically validated tools with impressive accuracy rates: 88% for Horizontal Gaze Nystagmus (HGN), 79% for Walk and Turn, and 83% for One Leg Stand, according to the widely cited San Diego study.

However, a closer examination of the research reveals a more complex picture. The same study that produced these frequently cited accuracy rates also had substantial false positive rates that are rarely discussed in training materials or courtroom testimony. These false positive rates—the percentage of times the tests incorrectly indicate that a person will be at/or above the legal limit of 0.08 g/dL, but the person is actually below the legal limit—have profound implications for how we interpret SFST results.

For members of the International Association of Forensic Toxicology Consultants (IAFTC), understanding the actual capabilities and limitations of the SFSTs is essential. The disconnect between how the SFSTs are portrayed in law enforcement training versus what the study data demonstrates creates significant challenges for scientific testimony and case interpretation.

This article serves multiple purposes for IAFTC members and the broader forensic community. First, it provides a review of the SFST development and validation, tracing these tests from their origins through current research. Second, it examines the false positive rates documented across multiple studies, including recent research that appears to have gone largely unnoticed in the law enforcement community. Third, it offers a detailed analysis of proper test administration procedures and common errors that may further compromise test validity. Finally, it addresses a critical limitation that is often misunderstood: according to the authors of the San Diego Study, these tests have only been validated to predict if a person's BAC is at or above a specific threshold—they have not been validated as indicators of driving impairment or alcohol/drug impairment.

As forensic professionals, there is a responsibility to ensure that scientific evidence is accurately represented and properly interpreted. The SFSTs remain a valuable screening tool for law enforcement, serving their intended purpose of helping officers make Probable Cause determinations during roadside investigations. However, when these tests are presented in court as proof of impairment, or when their limitations are not fully disclosed, we risk compromising the integrity of the forensic sciences and potentially contributing to wrongful convictions.

This article draws from National Highway Traffic Safety Administration (NHTSA) training manuals [4], original validation studies, the SFSTs Field Validation Studies (1995-1998) [5–7], and recent peer-reviewed research to provide IAFTC members with a more complete understanding of what the SFSTs can and cannot tell us about driver impairment. Whether you serve as an expert witness, conduct toxicological analysis, or work in research and policy development, this information is essential for ensuring that field sobriety test evidence is properly evaluated.

I. The Three Phases of DUI Detection

The First phase is “Vehicle in Motion.” Law Enforcement Officers are trained to look for 24 cues to indicate that a driver is possibly impaired. These include failing to maintain lane, driving without headlights, making wide turns, etc. When an officer decides to stop a vehicle, they are then trained to observe how the vehicle stops. The stopping sequence may provide the officer with additional evidence that the driver is possibly impaired. There are times in which the officer may not observe anything during Vehicle in Motion that makes them suspect that the driver is impaired (equipment violations, speeding, roadblock, etc.). During the next phase, the officer may see signs of possible impairment that lead to a DUI arrest.

The second phase is “Personal Contact.” This is probably the most important phase for two reasons. First, this is the only phase that is going to occur during every DUI investigation. Second, it is often the phase that a jury is going to put the most weight in because they are judging if the driver acts and looks the way they expect an intoxicated person to. In this phase, officers are trained to use their senses to identify indicators of possible impairment (bloodshot eyes, soiled clothing, fumbling fingers, open containers, slurred speech, admission of drinking, inconsistent responses, odor of an alcoholic beverage, cover-up odors, etc.). Officers are then trained to observe the driver’s exit from the vehicle. Do they leave the car in gear, use the car for balance, walk with a staggered gait, etc.? It is important to remember that by the end of this phase, an officer likely has probable cause to arrest the driver for DUI. 

The last phase is the “Pre-Arrest Screening.” This includes the Standardized Field Sobriety Tests (SFSTs) and the Preliminary Breath Test (PBT). Officers are trained to administer Horizontal Gaze Nystagmus (HGN), Walk and Turn, and One Leg Stand. After administering the SFSTs, officers can ask the driver to submit to a PBT. At the end of this phase, an officer decides whether they will arrest the driver for DUI based on the standard of Probable Cause. Officers are trained to base this decision on the totality of the circumstances, but in many cases, the arrest decision comes down to the results of the SFSTs.

II. Development of the SFSTs

Starting in 1975, the Southern California Research Institute (SCRI), with funding from the National Highway Traffic Safety Administration (NHTSA), began research studies to determine which roadside tests were the most accurate. Prior to this, officers were using tests, instructions, and clues that were not standardized between officers. This led to problems in court determining how much weight the tests should be given. The goal was to standardize the tests and observations and determine which tests were the most accurate at distinguishing Blood Alcohol Concentrations (BACs) at or above the legal limit. 

SCRI started with six field sobriety tests commonly used throughout the United States. These tests were: One Leg Stand, Finger to Nose, Finger Count, Walk and Turn, Alcohol Gaze Nystagmus (HGN now), and tracing (a paper and pencil exercise). The three most accurate tests are the ones we now know as the SFSTs. The Finger to Nose test is used as part of the Drug Recognition Expert (DRE) program, and the Finger Count is taught as a tool that can be used during Personal Contact [4].

The research included three Standardized Elements for the tests. The first is Standardized Administrative Procedures. Which means there is a required manner in which passes must be conducted for HGN, required instructions for each of the tests, and required demonstrations that must be given for the Walk and Turn and One Leg Stand. The second is Standardized Clues. This means officers are looking for specific clues during each one of the tests. The last is Standardized Criteria. This means that officers must observe a specific thing to count a clue. An example is to count missing heel to toe for the Walk and Turn; a person must miss heel to toe by one-half inch or more. NHTSA emphasizes that the validation only applies when the Standardized Elements are followed.

The Original Research determined how accurate each of the tests was at predicting if a person’s BAC was at or above 0.10 g/dL. When four or more clues were observed, HGN was 77% accurate. When two or more clues were observed on each test, the Walk and Turn was 68% accurate, and the One Leg Stand was 65% accurate. 

There were three field validation studies that were conducted between 1995 and 1998. The Colorado (1995), Florida (1997), and San Diego (1998) validation studies. The primary study that will be addressed is the San Diego study because it is the study that officers currently use to testify as to how accurate the SFSTs are. 

The San Diego study involved 297 drivers, and the mean BAC of those drivers was 0.122 g/dL [5]. Additionally, the mean BAC of the drivers who were arrested was 0.150 g/dL, and the mean BAC of those drivers not arrested was below 0.050 g/dL. Remember that the target BAC is 0.08 g/dL, so the further away from the target that you get, the more likely it is that it will be easier for an officer to make the correct decision. For example, a person who is two times the legal limit would be expected to show more obvious signs of intoxication than someone who is right at the legal limit. That most likely makes it easier for the officer to know an arrest is the correct decision to make. The officers in this study also had access to Preliminary Breath Tests (PBTs).

How accurate are the SFSTs based on the San Diego study? When four or more clues were observed, HGN was 88% accurate. When two or more clues were observed on each test, the Walk and Turn was 79% accurate, and the One Leg Stand was 83% accurate. The overall accuracy when the officers made their arrest decision was 91%. 

To understand exactly what this means, you need to understand what constitutes a “correct” decision and an “incorrect” decision. A “correct” decision was when a person was at or above the BAC level (0.08 g/dL) and the officer arrested them, or if the person was below the BAC level (0.08 g/dL) and the officer released them. An “incorrect” decision was when a person was at or above the BAC level (0.08 g/dL) and the officer released the person (false negative), or the person was below the BAC level (0.08 g/dL) and was arrested (false positive).

Remember, according to the authors of the San Diego Study, these tests have only been validated to predict if a person is at or above a specific BAC. They have not been validated as indicators of driving impairment or alcohol/drug impairment.

III. False Positives

What exactly is a false positive? It is a test that incorrectly indicates a condition exists when it in fact does not. An easy way to think of it is if you went to your doctor and your doctor ran some tests on you. Those tests came back and indicated that you have a disease, but you do not. Those tests would be a false positive. 

What were the false positive rates of the SFSTs from the San Diego study? HGN was 37%, Walk and Turn was 52%, One Leg Stand was 41% and when officers made their arrest decision, it was 28%. So, the Walk and Turn and One Leg Stand are about as statistically accurate as a flip of a coin if the person is below 0.08 g/dL. 

IV. Robustness of the Horizontal Gaze Nystagmus Test

This study was published in 2007 and was funded by NHTSA. Dr. Marceline Burns authored the study [8]. It was in reference to defense attorney arguments that if HGN was administered incorrectly, it would affect the validity of the test. It was conducted in a laboratory setting using volunteer drinkers and experienced officers.

There were (3) elements tested:

1. Stimulus Speed for Lack of Smooth Pursuit 

   1. Fast (1 second)

   2. Standard (2 seconds)

2. Stimulus Height 

   1. High (4 inches above eye level)

   2. Standard (2 inches above eye level)

   3. Low (0 inches - at eye level) 

3. Stimulus Distance

   1. Close (10 inches from the face)

   2. Standard (12-15 inches from the face)

   3. Far (20 inches from the face)

Looking at the results from the times in which HGN was administered correctly, the false positive rate was 67%. Additionally, 65% of the people below a BAC of 0.05 g/dL had four clues or more. There was a person with six clues at a BAC of 0.029 g/dL.

What about the times when the test was not administered correctly?

• Stimulus higher than the standard – 91% False Positive Rate

• Stimulus lower than the standard – 79% False Positive Rate

• Stimulus closer than the standard – 92% False Positive Rate

• Stimulus farther than the standard– 84% False Positive Rate 

These numbers show that it is imperative that officers position the stimulus correctly, or the false positive rates increase to even higher levels.

How did Dr. Burns address the extremely high false positive rates? She changed the standards to lower the number of reported false positives! In the current training material  (2025 Edition SFST Manual [9]) and in the San Diego Study, four or more clues correlated to a BAC of 0.08 g/dL or more. In this study, four clues correlated to a BAC of 0.03 g/dL or more. This drastically lowered the published false positives. There was no justification given for this changed standard. 

Read the rest of the article in PDF.

IAFTC Newsletter. Volume 1. Issue 1. October 3, 2025.

Aaron Olson¹  

¹ARO Consulting LLC, PO Box 132, Hugo MN, 55038

This is an open-access article under the CC BY-NC-ND license.

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Introduction

In June 2025, defense attorney Charles Ramsay and I published "Errors in toxicology testing and the need for full discovery" in Forensic Science International: Synergy [1]. Our review documented notable toxicology errors across multiple jurisdictions collected over a combined 48 years of field experience. 

This news article provides IAFTC members with brief updates on toxicology errors in the news since that publication.

Minnesota Breath Alcohol Testing: Control Target Error

In September 2025, Minnesota defense attorneys Charles Ramsay and I discovered that a DataMaster DMT breath alcohol analyzer had been operating with an unknown control target for nearly one year, from May 25, 2024, to May 4, 2025. The error occurred when an operator entered incorrect dry gas cylinder information during a Control Change test, resulting in 73 potentially invalid test results across multiple law enforcement agencies [2].

When the Minnesota Bureau of Criminal Apprehension (BCA) was confronted with this information, they acknowledged that their scientists cannot testify to the accuracy of these tests, stating that "BCA forensic scientists can only testify to the accuracy of test results with a known valid control target."

The BCA's internal quality controls missed this error for nearly an entire year. It took an independent review by defense counsel and outside experts to discover what should have been caught by basic quality assurance protocols.

Internal BCA emails reveal how the laboratory framed who was responsible for the error. In the nonconformity report, the BCA stated: "This is not the result of any work performed by the BCA Calibration Laboratory; it is the result of the agency entering incorrect information during the Control Change." 

Yet laboratory-level verification of Control Change data, a quality control step, should have been in place from the beginning.

Early notification drafts credited the defense attorney with discovering the error, but the final version removed this attribution. 

The first draft stated: "In a recent case, a defense attorney noticed that the dry gas cylinder referenced on a test record did not match the dry gas cylinder reported by the BCA to be installed in the instrument." 

The final notification sent to agencies simply stated: "It was discovered that the information associated with the installed dry gas cylinder for Instrument 100821...was entered incorrectly by an operator," removing any reference to how the error was actually discovered.

This pattern reinforces findings from our paper: laboratories often shirk taking responsibility for their errors and fail to recognize the need for independent outside auditors.

University of Illinois Chicago: THC Isomer Misidentification and Testimony Issues

In one of the most troubling cases of systematic evidence suppression, the University of Illinois Chicago Analytical Forensic Testing Laboratory (AFTL) knowingly used flawed testing methods for marijuana-impaired driving cases from 2021 through 2024 [3].

The laboratory's method could not distinguish between delta-9-tetrahydrocannabinol (Δ9-THC), the primary psychoactive compound in cannabis, and delta-8-tetrahydrocannabinol (Δ8-THC). This was important because the state's DUI law ties legal limits exclusively to Δ9-THC. Laboratory personnel became aware of these method deficiencies as early as 2021 but failed to disclose them until 2023, allowing hundreds of potentially wrongful convictions to proceed [4].

Figure 1. Δ8-THC, Δ9-THC, Δ10-THC. (Image credit: Mantinieks D, 2024; [5])

Injustice Watch revealed the harm caused to individuals by flawed testimony and testing. The report detailed how a lab analyst testified that THC metabolites in urine could be used to determine impairment, a claim that contradicts established toxicological science. The defense eventually called in renowned toxicologist Marilyn Huestis to testify against this type of testimony.

Approximately 1,600 marijuana-impaired driving cases were compromised. A 2025 prosecutorial review in DuPage County resulted in the dismissal of charges in 19 cases due to compromised evidentiary reliability [6].

University of Kentucky: Equine Testing Fraud

The September 2025 termination of University of Kentucky equine testing lab director Dr. Scott Stanley demonstrated how weak oversight enables systematic misconduct [7]. 

In November 2023, the Horseracing Integrity and Welfare Unit requested confirmatory analysis for a banned substance. Over the course of two months, Stanley repeatedly reported that the sample had been analyzed with negative results. 

On February 23, 2024, when HIWU inquired about remaining sample volume, lab staff revealed the sample "had never been analyzed and, in fact, had never even been opened." The university's audit found Stanley falsified results, failed to perform confirmatory analysis on 91 samples that screened positive.

The case revealed laboratory vulnerabilities. Weak internal controls gave all staff unrestricted data access while giving Stanley sole authority over communicating results to oversight agencies. 

Tennessee: Field Sobriety Test False Positives

Recent events in Tennessee illustrate the broader problems with the reliability of field sobriety testing [8]. Sixteen sober drivers were arrested for DUI by Tennessee state troopers in 2025, with eight arrests made by a single officer.

The most publicized case involved Jane Bondurant, a 71-year-old former U.S. Attorney, whose bloodwork came back clean except for prescribed medication taken the night before. Despite this, she was arrested, handcuffed, and jailed based on subjective field sobriety test performance.

These cases highlight the high false-positive rate associated with field sobriety tests [9].

Analysis: Recurring Patterns

These 2025 errors demonstrate the same patterns documented in our comprehensive review:

1. Extended Detection Times Errors persist for months or years before discovery (Minnesota: 1 year; UIC: 3 years).

2. External Discovery Problems are identified by defense attorneys, whistleblowers, or independent experts rather than internal quality controls.

3. Institutional Resistance Laboratories viewed transparency requests as hostile and developed cultures where concealment becomes normalized.

4. Systematic Impact: Individual errors affect dozens or thousands of cases before detection.

Implications for IAFTC Members

These cases underscore critical considerations for forensic toxicology consultants. Discovery requests must explicitly include all digital data and quality assurance documentation, not just final reports.

These errors highlight the ongoing need for laboratory culture reform, echoing the 2009 NAS report's recommendations [10]. IAFTC members should advocate for online discovery portals, mandatory retention of digital data, third-party audits beyond standard accreditation, and clear protocols for disclosure of discovery materials.

Conclusion

The toxicology errors documented in the months since our June 2025 publication continue to show the need for reform in forensic toxicology. These are not isolated incidents but manifestations of systemic vulnerabilities that persist across jurisdictions and disciplines.

For IAFTC members serving as expert witnesses, laboratory directors, or policy advisors, these cases underscore the importance of transparency, independent oversight, and cultural change within forensic laboratories. Scientific integrity requires more than technical competence; it demands institutional structures that make concealment impossible and accountability mandatory.

Conflicts of Interest

The author serves as an expert witness in forensic toxicology cases and receives compensation for speaking engagements.

AI Use Disclosure

The author used Claude (Anthropic) to assist with the organization and formatting of this article. All content was verified and substantially written by the author, who takes full responsibility for accuracy.

References

[1] Olson A, Ramsay C. Errors in toxicology testing and the need for full discovery. Forensic Sci Int Synerg 2025;11:100629. https://doi.org/10.1016/j.fsisyn.2025.100629.

[2] Knudsen C. Attorney discovers problem with alcohol detection device used in DWI cases in the heart of Minnesota’s cabin country. KSTP-TV LLC 2025. https://kstp.com/kstp-news/top-news/attorney-discovers-problem-with-alcohol-detection-device-used-in-dwi-cases-in-the-heart-of-minnesotas-cabin-country/   (accessed September 25, 2025).

[3] Dukmasova M. How a rogue Chicago forensics lab got people convicted for driving high. Injustice Watch 2025. https://www.injusticewatch.org/project/forensic-failures/2025/uic-forensics-lab-cannabis-dui-scandal/  (accessed August 14, 2025).

[4] Goudie C, Markoff B, Tressel C, Jones T. Chicago forensic testing lab accused of providing flawed results in marijuana DUI convictions. ABC7 Chicago 2024. https://abc7chicago.com/post/university-illinois-chicago-analytical-forensic-testing-laboratory-accused-providing-flawed-results-marijuana-dui-cases/15624653/  (accessed June 12, 2025).

[5] Mantinieks D, Di Rago M, Drummer OH, Glowacki L, Schumann J, Gerostamoulos D. Quantitative analysis of tetrahydrocannabinol isomers and other toxicologically relevant drugs in blood. Drug Test Anal 2024;16:1102–12. https://doi.org/10.1002/dta.3632.

[6] Rivera M, Tressel C, Markoff B, Jones T. DuPage County state’s attorney dismisses marijuana DUI charges after faulty blood tests. ABC7 Chicago 2025. https://abc7chicago.com/post/dupage-county-states-attorney-dismisses-marijuana-dui-charges-faulty-blood-tests-university-illinois-chicago-aftl/15851816/  (accessed June 12, 2025).

[7] Kuzydym S. University of Kentucky terminates former equine testing lab director. Louisville Courier Journal 2025. https://www.courier-journal.com/story/news/2025/09/11/university-of-kentucky-equine-testing-lab-director-terminated/86097262007/  (accessed September 13, 2025).

[8] Finley J. Former US attorney is 8th sober driver to be arrested for DUI by state trooper. WSMV 4 2025. https://www.wsmv.com/2025/08/28/former-us-attorney-is-8th-sober-driver-be-arrested-dui-by-state-trooper/  (accessed August 29, 2025).

[9] Kane G, Kane E. The high reported accuracy of the standardized field sobriety test is a property of the statistic not of the test. Law Probab Risk 2021;20:1–13. https://doi.org/10.1093/lpr/mgab004 .

[10] National Research Council, Division on Engineering and Physical Sciences, Committee on Applied and Theoretical Statistics, Policy and Global Affairs, Committee on Science, Technology, and Law, Committee on Identifying the Needs of the Forensic Sciences Community. Strengthening forensic science in the United States: A path forward. Washington, D.C., DC: National Academies Press; 2009. https://www.ojp.gov/pdffiles1/nij/grants/228091.pdf

Presentation Summary

On October 17, 2025, Dr. Stefan Rose will challenge retrograde extrapolation's scientific validity by focusing on an impossible requirement: knowing when and how much the pyloric valve opens to allow gastric contents to flow into the small intestine where the majority of alcohol absorption occurs—information unavailable without continuous physiological monitoring of multiple timed blood or breath samples starting at the beginning of the drinking episode.

The presentation will cover the complex factors controlling pyloric valve opening and closing: neural regulation (vagus nerve, myenteric plexus, splanchnic nerve), hormonal influences (gastrin, insulin, secretin, somatostatin, motilin, and other peptides), and external variables that delay gastric emptying and invalidate any retrograde extrapolation, including food, medications, trauma, surgery, and disease states like diabetes.

Dr. Rose argues that because pyloric valve status at any point in time of a drinking episode cannot be determined retroactively, retrograde extrapolation is fundamentally flawed and dubious, and addresses why analytical chemistry training has overshadowed comprehensive pharmacological education in the field.

About the Presenter

Dr. Stefan Rose is a physician with over 40 years of experience spanning Forensic Toxicology, Clinical Pathology, and General Psychiatry. He completed formal Forensic Toxicology training at the Dade County Medical Examiner Department (1989-1991), founded the first DUI laboratory at the University of Miami (1992), and completed psychiatric residency (1995-1998), where he correlated behavioral effects of drugs and ethanol with laboratory findings. He has served as a courtesy professor in Chemistry at FIU since 1997, is Board Certified by the National Board of Medical Examiners, and has extensive expert testimony experience in state, federal, civil, and criminal courts.

Join us

This presentation is for members only. Consider joining us to attend future webinars.

The International Association of Forensic Toxicology Consultants (IAFTC) is excited to announce the launch of our professional newsletter and invites members to submit their work for publication.

This is an exceptional opportunity to gain publication credit in a peer-reviewed professional organization newsletter and share your expertise with colleagues across the field.

Publication Timeline

Articles will be published on a rolling basis as soon as they complete peer review and are ready for press. Your work will appear on our website immediately upon acceptance rather than waiting for a traditional issue release date.

Types of Submissions We're Seeking

We welcome diverse contributions including:

• Case Studies - Real-world applications, challenges, or outcomes from your practice
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We accept submissions in free format, which means you have flexibility in how you structure and present your work. You're not required to follow a rigid template or specific journal style—write in the format that best suits your content and focus on clear communication.

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All submissions should include:

• Title - Clear and descriptive
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• Introduction - Context for why your topic matters
• Main content - Well-organized sections with appropriate headers
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• AI Use Disclosure - Statement regarding use of artificial intelligence tools (see below)

Transparency and Disclosure Requirements

Conflicts of Interest Statement

All authors must disclose any financial or personal interests that could be perceived as influencing their work. This promotes transparency and maintains the integrity of published research.

What to disclose:

• Employment relationships (including government laboratory employment)
• Consulting arrangements or expert witness work
• Research funding sources
• Financial interests in companies or products discussed
• Personal relationships that might present conflicts
• Any other circumstances that could be perceived as influencing objectivity

Example disclosure: "Dr. Smith serves as an expert witness in DUI cases and is employed by [Laboratory Name]. This work was partially funded by [Grant Source]."

Acknowledgements

Authors should acknowledge individuals or organizations that contributed to the work but do not meet authorship criteria.

What to include:

• Technical assistance or data collection support
• Funding sources or grants
• Institutional support
• Colleagues who provided feedback or review
• Any other substantive contributions

Example: "The authors thank [Name] for technical assistance with laboratory analysis and [Institution] for providing access to case files. This work was supported by [Funding Source]."

AI Use Disclosure

As artificial intelligence tools become increasingly prevalent in scientific writing, IAFTC requires transparency regarding their use.

Authors must disclose:

• Use of AI tools (e.g., ChatGPT, Claude, Grammarly AI, etc.) for any aspect of manuscript preparation
• Specific ways AI was used (literature search, writing assistance, data analysis, editing, etc.)
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Important: Authors remain fully responsible for the accuracy and integrity of all content, regardless of AI assistance. AI-generated content must be verified for accuracy and properly cited where applicable.

Example disclosure: "The authors used [AI Tool Name] to assist with grammar checking and initial literature organization. All content was verified and substantially revised by the authors. No AI-generated content appears without author review and validation."

File Format

Submit your work in any of the following formats:

• Microsoft Word (.docx)
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Use standard fonts (Times New Roman, Arial, Calibri) in 11 or 12-point size.

Peer Review Process

All submissions undergo peer review to ensure quality and accuracy while maintaining the high professional standards expected of IAFTC publications. Our editorial team will work collaboratively with you on any necessary revisions.

General announcements will not be peer reviewed.

Why Submit?

✓ Publication credit in a professional organization newsletter
✓ Be among the first authors featured in our inaugural volume
✓ Share your expertise with colleagues across the field
✓ Build your professional portfolio with peer-reviewed publication
✓ Contribute to the community by advancing knowledge in forensic toxicology
✓ Immediate visibility through rolling publication on our website

Ready to Submit?

Whether you're an established practitioner, researcher, or emerging professional, we encourage you to share your knowledge and experience. Your contributions will help establish this important platform for professional development and knowledge sharing within our field.

Submit your article or questions to:
editor@iaftc.org

Questions about topics or submission process?
Contact editor@iaftc.org - We're happy to discuss ideas before you submit!

Tips for Success

• Choose a topic you're knowledgeable about and passionate about
• Write clearly for a professional audience
• Support your points with data, examples, or case details
• Organize logically with headers and clear sections
• Cite your sources using any consistent academic format
• Don't worry about perfection - Our editorial team is here to help

Examples of Potential Topics

Not sure what to write about? Here are some ideas to spark your thinking:

• Challenges you've encountered in case work and how you addressed them
• New technologies or methods you've implemented in your laboratory
• Analysis of trends you're seeing in drug testing or toxicology results
• Quality assurance issues and solutions
• Interpretation challenges in complex cases
• Updates on regulatory changes or standards
• Conference highlights or continuing education insights
• Validation studies or method comparisons
• Expert witness experiences and lessons learned

Join Us in Creating Something Special

The IAFTC Newsletter represents a new platform for our professional community to share knowledge, discuss challenges, and advance the field of forensic toxicology and related disciplines. Your contribution will help establish the tone and quality of this important resource.

We look forward to featuring your work!