The DUI Evidence Against You Can Be Challenged — Murrieta’s Trusted DUI Defense Firm
Most people charged with DUI assume the evidence is what it is. A breathalyzer gave a number. An officer wrote a report. The field sobriety tests were recorded. What’s left to argue? Quite a bit, as it turns out. The evidence in a DUI case comes from equipment, human observation, and scientific procedures — all of which are subject to error, documentation requirements, and constitutional constraints. At the Law Office of Nic Cocis, challenging DUI evidence is central to every case we handle in Murrieta and Southwest Riverside County.
The Three Categories of DUI Evidence — and How Each Is Challenged
Officer Observations: Subjective and Contestable
The DUI case often begins with the officer’s account of the stop and the roadside encounter. The driving pattern observed, the odor of alcohol, bloodshot eyes, slurred speech, performance on field sobriety tests — these are the building blocks of the prosecution’s case before a chemical test is even administered.
Every one of these observations is subjective. Driving patterns consistent with DUI are also consistent with distraction, fatigue, unfamiliarity with the road, and medical conditions. Bloodshot eyes follow from allergies, fatigue, contacts, and smoke as readily as from alcohol. The standardized field sobriety tests — the horizontal gaze nystagmus (HGN), the walk-and-turn, and the one-leg stand — have documented false positive rates and require strict administration protocols. An officer who didn’t administer the tests correctly, who didn’t account for the roadside surface or lighting conditions, or whose training records don’t reflect current NHTSA certification produces testimony that can be challenged.
The officer’s body camera is evidence too — not just the report. The footage often tells a different story than the written account, and we request it in every case.
Field Sobriety Tests: Protocol Matters
The three standardized field sobriety tests validated by NHTSA have specific administration requirements, and officers who deviate from those requirements undermine the tests’ evidentiary validity. The HGN test requires specific instruction language, a specific stimulus distance, and a specific number of passes. The walk-and-turn requires a specific surface and a specific set of demonstrated instructions. The one-leg stand requires a specific timing method and specific safety conditions.
Beyond protocol, several physical conditions affect FST performance independent of intoxication: inner ear disorders, back injuries, knee problems, obesity, age, and fatigue all impair balance and coordination. Roadside conditions — uneven surfaces, inadequate lighting, traffic noise, weather — affect performance as well. We obtain the officer’s training records and administration logs in every case where FST evidence is central to the prosecution.
Chemical Testing: Equipment and Procedure
The breath and blood testing issues — calibration records, the 15-minute observation period, partition ratio variability, blood sample preservation — are covered in depth in our breath and blood test page. The short version: a BAC number from a breath or blood test isn’t self-proving. The equipment, the procedure, and the handling of the sample all affect the result’s reliability, and all of it is discoverable.
The Suppression Motion: When the Stop Itself Is the Issue
If the officer lacked reasonable suspicion to initiate the stop, or lacked probable cause to arrest, everything that followed — the field sobriety tests, the breath test, the arrest — may be suppressible under the Fourth Amendment’s exclusionary rule. A motion to suppress asks the court to exclude evidence obtained through an unlawful stop or arrest. If the motion succeeds and the core evidence is excluded, the prosecution often can’t proceed.
The standard for reasonable suspicion is not high — but it is a standard. Weaving within a lane, slightly wide turns, a brief stop sign roll that the officer later can’t document, or a traffic violation that turns out not to have occurred are all grounds on which suppression motions have succeeded. We evaluate the stop for constitutional validity in every DUI case.
How We Build a Challenging DUI Defense
01
Evidence Inventory
We identify every piece of evidence the prosecution intends to use: the police report, the dashcam and bodycam footage, the FST documentation, the breath or blood test records, and any witness statements. The full picture precedes any strategy.
02
Constitutional Analysis
We assess the legality of the stop, the lawfulness of the field sobriety test administration, and the constitutional validity of the arrest. If any stage was constitutionally deficient, we file a suppression motion.
03
Scientific Scrutiny
Calibration records, maintenance logs, observation period documentation, and blood test chain of custody are reviewed. Independent expert consultation is engaged where the analysis warrants it.
04
Trial or Negotiation
A defendant who walks into plea discussions knowing exactly what the prosecution can prove and what it can't negotiate from a completely different position than one who doesn't. Where the evidence can be challenged successfully at trial, we try the case.
Why Choose the Law Office of Nic Cocis?
Evidence-First Approach
Every case starts with a full review of the prosecution’s evidence — not a generic strategy
Former DA’s Office Intern
Knows how prosecutors evaluate DUI evidence and where they expect it to be challenged
25+ Years of DUI Defense in Riverside County
Extensive experience across misdemeanor and felony DUI matters
Multilingual Services
English, Romanian, and Spanish available
Frequently Asked Questions
Facing DUI Evidence in Murrieta?
The evidence isn't always what the prosecution says it is. Contact the Law Office of Nic Cocis for a consultation. We serve clients in Murrieta, Temecula, Menifee, Lake Elsinore, Wildomar, Winchester, Canyon Lake, French Valley, and throughout Southwest Riverside County.
