How to Challenge a Field Sobriety Test in Court

What counts as a “standardized” field sobriety test?

Per NHTSA, SFSTs comprise HGN, WAT, and OLS. Each has scripted instructions, precise clues, and specific scoring. The validation research underlying SFSTs assumes officers follow that script. If the officer departs from NHTSA’s steps—or the scene conditions don’t match training—the reliability drops and the evidence becomes easier to impeach. See NHTSA SFST Manual and Instructor Guide.

Core attack points that persuade judges and juries

• Officer qualifications: When and where was the officer last trained/refreshed on SFSTs? Cross on NHTSA’s required cues, demonstration steps, and timing. (NHTSA manuals detail each step.)
• Instruction errors: Omitted or altered instructions (e.g., WAT “nine heel-to-toe steps,” specific turn, arms at sides; OLS “count out loud,” “foot six inches off the ground”) undermine “standardization.”
• Environment & footwear: Uneven/soft surfaces, poor lighting, wind, wetness, traffic, or heels/boots can create “clues” unrelated to impairment—contrary to NHTSA assumptions for test conditions.
• Medical/neurological factors: HGN can be influenced by certain eye/vestibular issues and medications; musculoskeletal limits affect WAT/OLS. Demand medical review and video if available.
• Cue inflation & scoring drift: Press the officer on each recorded clue; many reports paraphrase results instead of documenting discrete NHTSA cues.

Linking roadside errors to later evidence

SFST flaws often cascade. A bad roadside leads to a questionable arrest decision, which taints the implied-consent advisement and any breath/blood collection that follows. California’s Title 17 (forensic alcohol analysis) imposes strict requirements on breath device maintenance, solution certifications, and blood draw protocols; use roadside errors to heighten scrutiny of later steps. See 17 CCR (Breath Alcohol Testing) and related Articles.

Voluntary vs. mandatory: avoid the common trap

In California, implied consent requires post-arrest chemical testing (breath/blood). It does not mandate pre-arrest SFST participation. Keep the record clean: note that the officer requested “field tests,” clarify conditions, and ensure any refusal or performance is accurately documented. Then, protect the DMV side by requesting the APS hearing within about 10 days of notice. Statutes and guidance: VC §23612; DMV APS overview.

How we build your SFST challenge

• Video & reports: Secure body-worn/dash video, audio, and all narrative/supplemental reports; compare to NHTSA scripts side-by-side.
• Training & maintenance records: Subpoena officer’s SFST training dates/scores and (if breath/blood followed) Title-17 device logs, solution certs, and chain-of-custody.
• Scene recreation: Photograph/measure test surface, slope, lighting, weather, and footwear; use this to impeach “standardized” conditions.
• Medical review: Document conditions (vertigo, knee/ankle issues, eye disorders) and medications that mimic SFST “clues.”
• Motions & cross: File to suppress where appropriate; in trial, cross on each missing NHTSA element and the officer’s scoring inflation.

FAQs

Are SFSTs “accurate”?

NHTSA validation studies support SFST use when administered as trained, but emphasize standardized instructions, scoring, and conditions. Accuracy varies by study and conditions—another reason to scrutinize how your test was done. See the NHTSA manual and field validation research.

Can I refuse SFSTs in California?

There’s no statute compelling pre-arrest SFSTs; implied consent applies to post-arrest chemical tests. Handle refusals carefully and preserve your DMV hearing rights. See VC §23612 and DMV APS.

What if I have a medical condition?

Medical and mobility issues can explain “clues” on WAT/OLS and eye conditions can affect HGN. Bring documentation; we incorporate it into motions and cross.

Do SFST errors help with the DMV case?

Yes. The same factual record supports both the APS hearing and the court case. We coordinate strategy so weaknesses in SFSTs carry through to license defense.

Talk with Braden & Tucci

We align NHTSA-grounded cross-examination with Title-17 discovery and DMV timelines to protect your license and your case. 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.