We had two DWI trials in the last two weeks where Standardized Field Sobriety Tests (SFSTs) were the central focus of the case. Field sobriety tests are among the most commonly used pieces of evidence in Minnesota DWI cases, but they are far from bulletproof. Because no Minnesota statute specifically governs FST admissibility, the entire framework rests on case law, the Minnesota Rules of Evidence, and prong II of the Frye-Mack scientific reliability standard. Understanding how these tests can be challenged is essential for anyone facing a DWI charge.
How Minnesota Courts Handle SFST Admissibility
Unlike chemical breath tests governed by Minnesota’s implied consent framework, field sobriety tests occupy a statutory gap. Minnesota’s DWI statute criminalizes driving under the influence but never mentions SFSTs. This means admissibility is determined through the Minnesota Rules of Evidence and judicial interpretation rather than any single statute.
Three rules of evidence carry the most weight in FST challenges. One governs expert testimony and triggers the Frye-Mack standard for novel scientific evidence, requiring general acceptance in the relevant scientific community, and whether the testing was administered in a reliable manner. Another permits lay opinion testimony based on a witness’s perception. A third allows exclusion of relevant evidence when its probative value is substantially outweighed by unfair prejudice. Minnesota Supreme Court precedent has established that each rule plays a different role depending on the type of test being challenged.
Standardized vs. Non-Standardized Tests
Not all field sobriety tests face the same legal hurdles, and defense strategies must account for the category each test falls into.
The Horizontal Gaze Nystagmus test is the most scientific of the three NHTSA-standardized tests, which involves observing involuntary eye movements as a stimulus crosses the subject’s field of vision. The Minnesota Supreme Court has held that HGN satisfies the Frye standard as a generally accepted indicator of impairment. Because of its scientific foundation, the prosecution must demonstrate that the administering officer had proper training and followed NHTSA protocol. Officers may not testify about a correlation between HGN clues and a specific blood alcohol level.
PRO-TIP! Whenever the State intends to offer testimony concerning an eye test known as the Horizontal Gaze Nystagmus (“HGN”), our firm requests that the Court give a cautionary jury instruction regarding HGN evidence. Minnesota law permits opinion testimony based on nystagmus testing only within limits. In State v. Klawitter, the Minnesota Supreme Court held that opinion testimony based on nystagmus testing is admissible “if a sufficient foundation has been laid for the opinion expressed and provided that the trial court, when requested, gives an appropriate cautionary instruction.” State v. Klawitter, 518 N.W.2d 577, 585–86 (Minn. 1994).
The state typically objects. It typically claims that Klawitter is “old” and “we never do that.” Unfortunately, this is because most DWI defense lawyers are unaware of Klawaitter’s provision requiring judges to read a special instruction to the jury about the HGN test.
The Walk-and-Turn and One-Leg Stand tests are considered observational measures of balance and coordination rather than scientific tests. They do not require Frye-Mack analysis and are admissible as trained officer observations, though they remain vulnerable to challenge on multiple grounds. In a trial earlier this week, we demonstrated the officer’s obvious lack of knowledge and asked the court to strike the officer’s SFST testimony in its entirety!
Non-standardized tests such as finger-to-nose, alphabet recitation, and the Romberg balance test carry significantly less weight because NHTSA has never validated them, making them particularly susceptible to exclusion.
NHTSA Protocol Deviations as a Defense Tool
The NHTSA DWI Detection and Standardized Field Sobriety Testing manual is one of the most powerful defense tools available. It states that if any element of a standardized test is changed, the validity of the results is compromised. The manual further specifies that SFSTs must be administered exactly as outlined each time they are given. Specifically, the provision states,
It is necessary to emphasize this validation applies only when the tests are administered in the prescribed and standardized manner, the standardized clues are used to assess the subject’s performance, and the standardized criteria are employed to interpret that performance. If any one of the SFST elements is changed, the validity may be compromised.
Common deviations that undermine reliability include moving the HGN stimulus too quickly, failing to hold it at maximum deviation for the required four seconds, administering balance tests on uneven or slippery surfaces, and not timing the One-Leg Stand for a full 30 seconds. NHTSA also acknowledges that individuals over 65, more than 50 pounds overweight, or with leg, back, or inner ear conditions should only receive the HGN test.
While Minnesota courts generally treat protocol deviations as affecting the weight of FST evidence rather than its admissibility, the Frye-Mack standard’s second prong requires proof that administration in a particular case conformed to procedures necessary to ensure reliability. Substantial deviations can undermine that foundation enough to warrant exclusion entirely.
The Ramsay Law Firm attorneys have been trained and certified by a National Highway Traffic Safety Administration (NHTSA) instructor for Standardized Field Sobriety Tests, ARIDE, and Chuck Ramsay is even a certified SFST instructor! In fact, we believe we are the best trained DWI lawyers in Minnesota. And for this reason, may be Minnesota’s Best DWI lawyers.
Common Grounds for Suppressing FST Evidence
Several legal arguments have proven effective in keeping FST evidence out of Minnesota DWI trials.
An unlawful traffic stop is the broadest challenge. If the initial stop lacked reasonable articulable suspicion, all evidence flowing from it must be suppressed under the exclusionary rule. Minnesota’s constitution provides broader protections than the federal Fourth Amendment, and Minnesota courts have held that each incremental intrusion during a stop must be independently justified.
Medical conditions also provide a strong basis for exclusion. Nystagmus can result from inner ear diseases, neurological conditions, certain medications, and fatigue. Balance-test failures stem from back, hip, and knee injuries, neuropathy, and age-related decline. Officers are trained by other officers rather than medical professionals and cannot determine whether nystagmus is caused by alcohol or an underlying condition.
Environmental factors are especially relevant in Minnesota. Ice, snow, extreme cold, wind, poor lighting, and flashing patrol car lights can all compromise test validity and provide strong grounds for exclusion.
Insufficient officer training is another avenue. Officers must complete NHTSA’s 24-hour training course, but the agency issues no formal certification. Challenging whether training is current and whether the officer can properly demonstrate procedures can undermine the evidentiary foundation.
The Contested Omnibus Hearing: Where SFST Challenges Are Decided
Minnesota’s primary vehicle for challenging SFST evidence before trial is the omnibus hearing, which must be scheduled within 28 days of the defendant’s first court appearance. When suppression issues are raised, the hearing becomes a contested omnibus hearing where the officer testifies, the defense cross-examines, and the court rules on admissibility.
The procedural stakes are significant. Under Minnesota’s criminal procedure rules, failure to raise known issues at the omnibus hearing waives them for later stages. Defense attorneys also file motions in limine closer to trial to exclude specific SFST evidence or limit officer testimony. The State bears the burden of proving evidence was lawfully obtained.
Why Experienced DWI Defense Counsel Matters
Challenging field sobriety test evidence requires more than general criminal defense knowledge. It demands familiarity with NHTSA testing protocols, the ability to identify subtle deviations from procedure, command of the Frye-Mack standard, and experience cross-examining officers on their training and techniques. An experienced Minnesota DWI lawyer knows how to review body camera and dashcam footage for inconsistencies, raise the right challenges at the omnibus hearing before rights are waived, and present medical and environmental evidence that undermines the reliability of SFSTs. In a legal landscape shaped by case law rather than statute, skilled DWI defense counsel can mean the difference between evidence that reaches the jury and evidence that never sees the inside of a courtroom.
