typewriter - guilty until proven innocent

A model evidentiary policy

Field Sobriety Tests (FSTs) and Standardized Field Sobriety Tests (SFSTs) as Pseudoscience

US-Centric (manufactured probable cause)

This model evidentiary policy supplements Guilty until proven innocent (never plead guilty), Until proven innocent - the process, and Police stops. This describes police traffic stops targeting impaired driving.

These are general comments about US criminal process. Other countries of course have different requirements. This is particularly the case with impaired driving, because the US and a few other countries have probable cause requirements[1] [2] for requiring a chemical test for impairment. Without probable cause, the chemical test results cannot be introduced in a court of law under the Exclusionary Rule. ("probable cause" and "Exclusionary Rule" are US terms. Terms in other countries may differ.[1] [2])

Submission of FSTs as evidence are a dead-on indication that Probable Cause is lacking.

Field Sobriety Tests (FSTs) are well-known as a substitute for articulable Probable Cause. As pseudoscience, FSTs have never been peer-reviewed and present no rational basis for assertion of comparison with a baseline reference for the suspect.

If probable cause for arrest is required, this should be directed to tangible observations without the use of pseudoscience. (It is likely that "tangible observations" will need to be something more than "standard three" common canned observations of "watery eyes", "smell of alcohol", "slurred speech".)

Rephrased, if a key element of Probable Cause evidence is pseudoscience, there is no Probable Cause. For adjudication purposes, it's important to avoid the "beg the question" fallacy of what the FSTs are appear to show. FSTs are either valid evidence or pseudoscience,

The difficulty, at least during adjudication, is that pseudoscience is largely misunderstood, or rather only vaguely understood.

Pseudoscience and Lack of Peer Review

Pseudoscience has a wide variety of definitions, but fortunately the different definitions are pretty much in alignment.

the Standardized Field Sobriety Tests (SFSTs) are widely considered to be pseudoscience for a number of reasons:

The lack of peer review is particularly poignant, given that the NHTSA asserts peer review, showing (on its instruction outlines) an image of a scientific article (possibly the SCRI report itself) but without attribution, with the obvious implication that the unattributed image somehow demonstrates actual peer review.

One would reasonably expect that no judge would allow FST evidence in either an evidence suppression hearing or any other judicial proceeding. The problem is that most judges are not trained in peer-reviewed scientific tests, and therefore tend to accept this pseudoscience as having some kind of probative meaning. (The benefit to the citizen is that, if a judge or magistrate is used to accepting FSTs as probative, that judge or magistrate will be less inclined to consider actual observations to have substantive meaning.)

The issue

Despite the fact that FSTs are outright pseudoscience, the very promotion of FSTs as having meaning has made it difficult for courts and administrators to deem FST evidence inadmissible (or admissible to demonstrate that an attempt to introduce FST evidence is effectively an admission that articulable evidence of probable cause is lacking). This is complicated by the fact that judicial and administrative are not scientists or researchers trained to recognize pseudoscience -- i.e., "If it is presented as measuring something, it must be valid."

It is therefore incumbent on the judge or administrator to make a determination that FST evidence is pseudoscience, essentially used to obfuscate the lack of articulable evidence supporting probable cause.

Courts and Administrators - Specific reasons for exclusion

This is relevant to administrators and judicial officers in criminal and quasi-criminal hearings. As a practical matter, "It's pseudoscience" could be considered conclusionary. Obviously, dismissing FST evidence out-of-hand could go against written or unwritten policy of a judicial or enforcement entity. Therefore, specific articulable reasons for disregarding FSTs and other pseudoscience are preferable.

While pseudoscience per se should be carte blanche excluded as evidence, it is often necessary to provide articulable reasons for exclusion of FST evidence beyond the bare assertion of "pseudoscience". The following are specific issues raised by FSTs:

FSTs (including SFSTs) have never been peer reviewed.

The FSTs have no reference baseline, and therefore cannot reasonably be used to evaluate a suspect's condition.
If the results of a FST test (or exercise) are such that the subject's impairment is obvious, the impairment would be apparent from ordinary interactions with the subject.

FSTs do not provide a means to "take into account" the subject's abilities or disabilities.

The instructions for FSTs (notably the Walk-and-Turn Test) begin the procedure before providing complete instructions.[6] . As a result, a subject having difficulty trying to maintain balance would be unable to properly comprehend the instructions. This fault has never been corrected (in part because the SCRI is now defunct).
This "interrupted procedure" makes it impossible to evaluate task completion and in particular precludes the evaluation of "divided attention". This fault is not fully obvious when reviewing videos or testimony regarding the subject's performance of the test.

The instructions for FSTs include substantial ambiguities.
Examples are the meanings of instructions, the frequently-used "imaginary lines" and ambiguous turning instructions. In addition, some of the instructions are based on interpretation of semantics.

In the case of disability of the subject, the scoring of "clues" provides no way to "take into account" the disability.

The police may have requested performance of FSTs without advising that the request is subject to Miranda protections.
In most cases, the police "accidentally" forget to advise that performance of FSTs is entirely voluntary. Some procedures give the reason is "to dispel my suspicions" or to "see if you are safe to drive", rather than to generate the (superficial) appearance of probable cause evidence.

Evidentiary standards

While the Frye standard (CA, IL, MN, NY, PA, WA) is more ambiguous than the Daubert standard and Federal Rules of Evidence §702 used in most other jurisdictions, pseudoscience should be excludable regardless of the standard for the same reasons lie detector evidence is excludable.

As mentioned above, FSTs (including SFSTs) have never been peer reviewed, and have no reference baseline.

Defense strategy

The defense strategy is essentially the same, which is to assert that the attempted use of FSD evidence itself is an attempt to introduce pseudoscience as probable cause, as an admission that articulable evidence of probable cause is lacking:

  1. Introduces or emphasizes the assertion that FSDs are pseudoscience rather than credible evidence (i.e., have never been peer reviewed, and have no reference baseline) ;

  2. Argues that the "clues" and other conclusions presented by FSDs lack credibility;

  3. Suggests that articulable probable cause observations are lacking, so that subsequent evidence should be excluded under the Fourth Amendment (US Constitution);

  4. Presents the assertion that the police request that the defendant perform FSDs are an indication that the police lacked probable cause for arrest;

  5. Presents the assertion that the prosecution attempt to introduce pseudoscience as probable cause is effectively an admission that articulable evidence of probable cause is lacking;

  6. Presents a focus for subsequent arguments attacking FSD evidence; and

  7. Provides the judge or administrator with a basis for excluding FSD evidence (as pseudoscience) and for limiting evidence to articulable observations.

The term "pseudoscience" should be included in order to place arguments relating the the FSTs into context. This also presents an argument that attempted use of FST evidence as an admission that articulable probable cause does not exist, and provides the judge or administrator a basis for exclusion.

There is also the possibility that the judge or administrator will recognise that he or she would not be able to "pass" these exercises, or otherwise understand the basic unfairness implied by the introduction of pseudoscience evidence.

Not legal advice

This is also not legal advice; it is general commentary on the internet. For legal advice and information outside of the US, please look up local law or speak with a lawyer. If speaking with a lawyer is not an option, locate a civil rights organisation in your jurisdiction such as (in the US) the ACLU. There are also quite a few attorneys with information on webpages.

Effect on DUI enforcement

Eliminating pseudoscience aa a basis for Probable Cause would result in more effective enforecement.

Exclusion of FST evidence of course eliminates using FSTs as a substitute for articulable Probable Cause. This would appear to restrict DWI arrests to instances in which articulable Probable Cause can be demonstrated, but by requiring articulable Probable Cause, the police are encouraged to identify offending drivers. This could make it more difficult to generate increased arrest statistics, but will result in removing more intoxicated drivers from the road. In other words, requiring the police to rely on articulable observations should result in more emphasis on police observation.

With routine use of police dash cams and body cams, articulable Probable Cause is easily obtained and reproduced for review by adjudicating authorities. Regardless, there was never a legitimate basis for the use of pseudoscience to allege Probable Cause for arrest.

Moreover, it is possible to identify an impaired driver by legitimate observation. The requirement for articulable probable cause for arrest is not justification for resorting to pseudoscience.

In many cases, if the suspect has a history of impaired driving convictions, confession and probable cause evidence obtained in the field is more-or-less an afterthought. The police already have probable cause from police records of convictions, which are easily combined with observations not requiring confessions, FSTs or PSTs.

More information

Police stops are described at

"busted" YouTube video
(45 minute video, but worth watching)

(same thing, in text)

The ACLU website


[1]^     Section 8 of the Canadian Charter of Rights and Freedoms protects against unreasonable search and seizure.

[2]^     Reasonable and probable grounds in Australia (Australian common law)

[3]^     The NHTSA Field Sobriety Test battery was commissioned, by the NTSB, to a defunct entity called the "Southern California Research Institute (SCRI)". This resolved the quandary of a series of even more silly FSTs, but it remains questionable how judges consider the NHTSA tests to be relevant to probable cause. These SCRI (NHTSA) tests have never been peer reviewed, although a few documents assert they are peer reviewed on the basis of the SCRI having self-reviewed their own "research". (i.e., they were never peer reviewed; but rather self-certified by the entity that produced the "research"!)  Basically the (defunct) SCRI entity converted bovine-sourced organic fertilizer to bovine-sourced organic fertilizer.
(For further information, see Law Office of Walter M. Reaves, Jr., P.C., - describing the science (or lack thereof) behind Field Sobriety Testing.)

[6]^     The SFST procedure for the "Walk and Turn" test has a glaring error that has never been corrected. The test procedure places the subject in a "starting position" of one foot in front of the other, requiring balancing skills. The procedure follows this with the officer's instructions and a partial demonstration. This of course places the subject trying to maintain balance rather than listen to instructions.

The result is that a person who isn't trained to balance in that manner will either focus on the balancing and therefore not comprehend the full instructions, or position out of the "starting position" focus on the full instructions. Either way, the image is the obvious -- not following the instructions. Unfortunately, this is not apparent to judges, who are not physically performing the test.

The NTSB and their (now defunct) contractor have never corrected this error.

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First written 16-Jun-24. Last revised 16-Jun-24. ~~ This page copyright 2024,
Stan Protigal - Comments about this site: email me

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