IAFTC Newsletter. Volume 2. Issue 2. May 21, 2026.

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 Seated Battery of Standardized Field Sobriety Tests (SFSTs) was developed for Boating Under the Influence (BUI) investigations, where balance-dependent roadside field sobriety tests are impractical. This article analyzes the two foundational studies supporting the Seated Battery: the laboratory development study and the field validation study. Reported accuracy, sensitivity, specificity, and false positive and false negative rates are examined for each individual test and for the combined battery. While some measures, most notably Horizontal Gaze Nystagmus and Finger to Nose, demonstrated improved specificity in the field, the combination of tests had a substantial decrease in sensitivity in the field, resulting in a false negative rate of 72%. This analysis raises significant concerns regarding officer selection, unexplained performance shifts between studies, and the suitability of the Seated Battery as a screening tool for BUI Investigations. The findings suggest that additional research and refinement are necessary before the Seated Battery of SFSTs can be relied upon as a scientifically valid method for identifying boaters with a blood alcohol concentration at or above 0.08%.

Introduction

Standardized Field Sobriety Tests (SFSTs) were originally developed for roadside enforcement to assist officers in identifying drivers whose blood alcohol concentration (BAC) is likely at or above a defined threshold.

The Walk and Turn and One Leg Stand tests rely heavily on balance, making them poorly suited for use in marine environments, where boat motion and residual “sea legs” can affect performance independent of intoxication.

To address these limitations, researchers developed the Seated Battery of Standardized Field Sobriety Tests for use in Boating Under the Influence (BUI) investigations. The Seated Battery consists of four tests, Horizontal Gaze Nystagmus (HGN), Finger to Nose (FTN), Palm Pat (PP), and Hand Coordination (HC), administered while the subject is seated. Like the roadside SFSTs, the Seated Battery was designed and validated to identify that a subject’s BAC is likely at or above 0.08%, not to measure impairment.

The scientific foundation for the Seated Battery rests on two studies: a laboratory development study and a field validation study. These studies reported varying levels of accuracy, sensitivity, and specificity across individual tests and the combined battery. While the authors concluded that the Seated Battery demonstrated sufficient reliability for operational use, closer examination of the data reveals substantial limitations, including high false positive rates in the laboratory, substantial shifts in performance between the laboratory study and the field study, unexplained and problematic reductions in sensitivity, and concerns related to officer selection.

This article critically examines both foundational studies, compares their reported performance metrics, and questions whether the Seated Battery meets the sensitivity that should be expected of a screening tool intended to identify operators who are at or above a BAC of 0.08%. 

Overview of the Tests

The Seated Battery of Standardized Field Sobriety Tests (SFSTs) was developed for Boating Under the Influence investigations due to the multiple issues of using tests that require balance for someone on a boat or who has recently been on a boat. (“Sea legs”)(1) 

There are (4) tests that are a part of the Seated Battery of SFSTs: Horizontal Gaze Nystagmus (HGN), Finger to Nose, Palm Pat, and Hand Coordination. Just like the standing SFSTs, these tests were only validated to indicate if a person’s Blood Alcohol Concentration (BAC) was likely at or above 0.08%.

Development of Sobriety Tests for the Marine Environment study (2)

This laboratory study involved 157 paid volunteers who were randomly assigned to one of four groups to be dosed with alcohol. (0.00, 0.04, 0.08, and 0.12%) There were twenty-four officers with an average of 9.7 years’ experience administering the roadside SFSTs. There were six tests evaluated: Finger to Nose (Finger to Nose), Time Estimation (TE), Finger Count (FC), Hand Coordination (HC), Palm Pat (PP), and Horizontal Gaze Nystagmus (HGN). To measure the volunteers' BAC, the Intox EC/IR and Alco Sensor FST were used. 

Results (BAC ≥ 0.08 vs < 0.08):

• HGN:Accuracy 67.4%Sensitivity 86.8%False Positive Rate 44.7%

• FTN:Accuracy 59.9%Sensitivity 58.5%False Positive Rate 39.3%

• PP:Accuracy 57.2%Sensitivity 66.0%False Positive Rate 48.2%

• HC:Accuracy 57.2%Sensitivity 64.2%False Positive Rate 47.1%

• Combination: Accuracy 72.3%, Sensitivity 81.1%, False Positive Rate 33.3%

• Time Estimation and Finger Count did not correlate with BAC and were excluded from the final battery.

The average BAC of the volunteers ≥0.08% was 0.102%.The average BAC < 0.08% was only 0.023%, yet false positive rates were high across all tests. The authors attributed the lower accuracy to lower overall BACs compared to prior SFST studies. While this explanation may account for reduced sensitivity, it does not adequately explain the high false positive rates at low BACs. Notably, raw data were not published, preventing analysis of false positives in the placebo group.

The authors noted, “the overall correct percentages, sensitivity, and specificity of the tests were below what is typically reported in the literature on the roadside SFSTs. Comparison with prior studies, however, should be made with caution. First, in this study, the average BACs were considerably lower than in previous studies. In the Burns and Moskowitz study, for example, 48 participants were tested at a mean BAC of 0.120%, and 16 participants were tested at a mean BAC of 0.156%. In comparison, in the current study, the highest BAC group was tested at a mean BAC of 0.110%. The wider distribution of BACs in the previous studies may have made the impairment or no impairment decision less difficult than in the current study.”

Despite officers’ experience, a large variability in performance was observed; 20% of officers were less than 50% accurate on HGN. 

The authors ultimately concluded the tests warranted field validation without any reported modifications to the tests.

Validation of Sobriety Tests for the Marine Environment (3)

This was a field study that was conducted on the Lake of the Ozarks in Missouri. Four marine officers from the Missouri State Water Patrol who had prior experience administering HGN were used for the study. In the Development Study, in which twenty-four officers were used, it was noted that there were great differences between the accuracy rates of the officers. That number was now cut down to only four, which creates questions about how the officers were selected and why the number of officers was reduced to four.

The officers in this study received an eight-hour class and then 3 ten-hour shifts in patrol boats on the water to become proficient with the tests. An inexperienced officer attending the National Association of State Boating Law Administrators’ (NASBLA) course receives only twenty-four hours of training when being taught how to administer and interpret these tests, and none of those hours are in patrol boats on the water.

During the study, officers stopped boaters suspected of BUI and asked them to come aboard the patrol boat. The Seated Battery of SFSTs was then administered. There were observers present during 76% of the study cases. The majority of the stops were Probable Cause stops involving a boater suspected of BUI by the officer, and the other stops were checkpoint stops. The study noted that some passengers were administered the tests, and their data were included in the analysis.

Average BACs:

• < 0.08%: 0.028%

• ≥ 0.08%: 0.133%

There were a total of 331 cases, and only one of those people refused to provide a blood or breath specimen. This means that only 0.3% of the people involved in the study refused to submit to chemical testing. This is an extremely low rate of refusals and matches the rate seen in the San Diego study(4).

Key Results:

• HGN:Accuracy 84.8%Sensitivity 86%False Positive Rate 16%

• FTN:Accuracy 67.3%Sensitivity 49%False Positive Rate 19%

• PP:Accuracy 65.2%Sensitivity 76%False Positive Rate 43%

• HC:Accuracy 59.4%Sensitivity 62%False Positive Rate 43%

• Combination: Accuracy 68.1%, Sensitivity 28%, False Positive Rate 2%

The false positive rate of the combination of all four tests dropped by 31.3% from where it was in the laboratory study.The false negative rate was 72%. This is alarmingly high. This means that over half of the BUI suspects who should be charged may be incorrectly released by officers. This is the opposite of what should be desired and accepted from field sobriety tests.

The author concluded, “It is proposed that marine officers administer HGN, FTN, PP, and HC to all BUI suspects, and then, for each suspect, use the pattern of test results to estimate the probability of BAC ≥. 08%.” 

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