Evidence in Drunk Driving Accident Cases: What Your Attorney Needs

Drunk driving cases produce more evidence than typical car accidents. The criminal investigation generates BAC results, field sobriety test recordings, dash cam footage, and officer testimony that does not exist in standard collision cases. Knowing what evidence to collect — and how to preserve it before it disappears — can make the difference between a full recovery and a compromised claim.

This article is part of our complete guide to drunk driving accident claims in Illinois. Here we focus specifically on the evidence that builds the strongest possible case.

Blood Alcohol Concentration (BAC) Evidence

BAC results are the single most powerful piece of evidence in a drunk driving case. Under 625 ILCS 5/11-501, a BAC of 0.08% or higher creates a presumption of impairment. But even lower BAC levels support a civil claim — Illinois recognizes that impairment begins well below the legal limit.

BAC evidence comes from breath tests (Breathalyzer), blood draws, and sometimes urine tests. Each has different reliability considerations. Blood draws are the most accurate. Breath tests can be challenged based on calibration, administration errors, or medical conditions. Your attorney may hire a toxicology expert to interpret the results and calculate retrograde extrapolation — estimating what the driver’s BAC was at the time of the crash based on the later test result.

Police Reports and Officer Observations

The responding officer’s report contains critical observations: the smell of alcohol, bloodshot eyes, slurred speech, unsteady gait, open containers in the vehicle, the driver’s statements at the scene, and the results of standardized field sobriety tests (walk-and-turn, one-leg stand, horizontal gaze nystagmus). These real-time observations are difficult for the defense to dispute later.

Request the police report as soon as possible. In Peoria County, reports are typically available within a few days. If dash cam or body cam footage exists, it must be preserved — departments have varying retention policies, and footage can be overwritten if no preservation request is made.

Surveillance and Traffic Camera Footage

Video evidence from the bar or restaurant where the driver was drinking, traffic cameras near the crash site, and nearby business security cameras can establish the driver’s condition before the crash. This evidence is especially critical for dram shop liability claims, where you must prove the establishment served the driver while visibly intoxicated.

Time is the enemy here. Most commercial surveillance systems overwrite footage within 7-30 days. Your attorney should send evidence preservation letters to all relevant businesses within days of the crash.

Bar and Restaurant Records

Credit card receipts, tab records, POS system data, and server notes document exactly what the driver consumed and when. These records establish the timeline of intoxication and identify which establishment bears dram shop liability. Subpoenas may be necessary to obtain these records if the establishment does not cooperate voluntarily.

Crash Reconstruction

In serious injury and fatality cases, a crash reconstruction expert can analyze vehicle damage patterns, skid marks (or the absence of skid marks — drunk drivers often fail to brake), final rest positions, event data recorder (EDR/”black box”) data, and road conditions to establish how the crash occurred and what the drunk driver was doing in the moments before impact.

Medical Records Linking Injuries to the Crash

Your medical records connect the accident to your injuries. Seek medical attention immediately — even if you feel fine at the scene. Emergency room records, diagnostic imaging, surgical reports, and rehabilitation notes all become evidence. Gaps in treatment give insurers ammunition to argue your injuries are not as serious as claimed or were caused by something else.

Witness Testimony

Other drivers, passengers, pedestrians, bar staff, and anyone who observed the driver before or after the crash can provide testimony. Bar employees who served the driver are particularly valuable witnesses. Their testimony about the driver’s condition establishes the “visibly intoxicated” element of a dram shop claim.

Frequently Asked Questions

How long do I have to preserve evidence after a drunk driving accident?

Act immediately. Surveillance footage can be overwritten within days. Police dash cam footage has varying retention periods. Bar receipts and records may be discarded. Contact an attorney within the first week after the crash to begin evidence preservation efforts.

Can BAC results from the criminal case be used in my civil claim?

Yes. BAC results, field sobriety test results, and other evidence from the criminal investigation are admissible in your civil case. Your attorney can obtain these through subpoena or by monitoring the criminal proceedings.

What if there is no BAC test because the driver refused testing?

A refusal to submit to BAC testing is itself evidence. Under Illinois implied consent law, refusing a breath or blood test results in automatic license suspension and can be used against the driver in both criminal and civil proceedings to suggest consciousness of guilt.

Talk to a Peoria Personal Injury Lawyer

Call (309) 672-9000 or contact us online for a free consultation. At Parker & Parker Attorneys at Law, we handle personal injury cases on a contingency fee basis — you pay nothing unless we recover compensation for you.