Common Police Mistakes During Field Sobriety Testing

1) Improper or incomplete instructions

NHTSA requires scripted instructions and an officer demonstration for WAT/OLS. Common lapses: skipping the demonstration, omitting the “nine heel-to-toe steps,” failing to explain the pivot turn, not telling the subject to keep arms at sides or count out loud. Any deviation undercuts “standardization.” Source: NHTSA SFST Manual.

2) Wrong surface or unsuitable conditions

Testing on sloped, gravel, wet, or debris-strewn surfaces contradicts training assumptions. Headlight glare, sirens, heavy traffic, wind, rain, or tight shoulders introduce balance and attention problems unrelated to alcohol.

3) HGN administration mistakes

HGN requires specific stimulus distance (~12–15 inches), height (slightly above eye level), smooth passes at prescribed timing, and proper check for equal tracking/maximum deviation/angle of onset. Common errors: moving the stimulus too fast, too close/far, or not holding at maximum deviation long enough. See NHTSA Instructor Guide.

4) Ignoring medical and footwear limitations

Back/knee/ankle injuries, age-related balance issues, inner-ear/vestibular disorders, neurological/eye conditions, and certain medications can mimic “clues.” High heels, boots, or restrictive clothing affect performance. NHTSA instructs officers to account for such factors—failure to screen or document them undermines reliability. NHTSA Manual.

5) Timing, pacing, and divided-attention errors

Officers must pace the test per training (e.g., HGN pass durations, WAT cadence) and avoid talking over the subject during performance. Command stacking or mid-test interruptions create divided-attention burdens not contemplated by the validation studies.

6) Qualification and refresh issues

If an officer’s SFST training is outdated or incomplete—or if they can’t articulate the NHTSA cues—courts give less weight to their opinions. Subpoena training records and lesson plans to test competency against the manuals.

7) Documentation gaps and video mismatch

Police reports often paraphrase results rather than listing specific NHTSA clues. Body-cam/dash-cam footage, scene photos, and measurement of slope/grade frequently contradict narrative claims. A side-by-side chart of “manual step” vs. “what the video shows” is persuasive for judges and juries.

Voluntary SFSTs vs. mandatory chemical tests

California’s implied-consent statute requires post-arrest chemical testing (breath/blood); it does not mandate participation in pre-arrest SFSTs. Keep these regimes separate and preserve DMV rights by requesting the APS hearing within about 10 days of notice. Statutes/guidance: VC §23612 · DMV APS.

How we prove these mistakes

• Discovery: body-cam/dash-cam, supplemental reports, scene photos, CAD logs; officer training/certification and lesson plans.
• Scene audit: measure slope/grade, surface type, lighting, weather, footwear; recreate vantage points and glare.
• Medical review: physician declarations on balance/vision/vestibular issues and medication side-effects.
• NHTSA cross-examination: walk through each manual step and clue; highlight every departure from standardization.

FAQs

Are SFSTs admissible if the officer didn’t follow the manual?

Courts can admit them but give reduced weight—or suppress derivative evidence—when administration deviates from NHTSA standards or conditions were unsuitable. Manuals: SFST Manual.

Can I refuse SFSTs in California?

Pre-arrest SFSTs are not mandated by statute; implied consent applies to post-arrest chemical testing. Handle refusals carefully; if arrested, protect DMV rights promptly. VC §23612 · DMV APS.

Do poor testing conditions help at the DMV hearing?

Yes. The same facts that impeach SFST reliability can undermine probable cause and support set-asides at the APS hearing.

Talk with Braden & Tucci

We align NHTSA-grounded cross-examination with scene audits and medical documentation to challenge SFSTs—and we run your DMV strategy in parallel. Call (949) 996-0170 or visit DMV Hearings and License Suspension to start your defense.

Disclaimer: This article is for general information only and not legal advice. Outcomes depend on specific facts and jurisdiction.