Proving a Truck Driver Was Impaired at the Time of an Accident

Accident victims who suspect a truck driver was impaired at the time of a truck accident must provide evidence of impairment. This evidence will vary depending on the type of impairment the victim suspects caused the accident. It might include test results, driver records, and more.

Types of Impairment & Evidence to Prove Impairment

Many people associate alcohol with impairment. Although it certainly causes impairment, that’s just one form of impairment. Anything that affects the driver’s ability to operate a motor vehicle in a safe manner could fall under impaired driving. Below are some types of impairment that may cause or contribute to a truck accident.


Truck drivers are not allowed to get behind the wheel of a big rig within four hours of consuming alcohol. The blood alcohol content (BAC) limit enforced by the federal trucking industry is 0.04. Alcohol testing is required after accidents that cause bodily injury or death. The results of the test are one way to prove intoxication. A citation and conviction for DUI could be evidence as well.


The same post-accident testing rules apply to drugs.

The five drugs the test covers are:

  • amphetamines;
  • marijuana;
  • phencyclidine (PCP);
  • cocaine; and
  • opiates.

As with an alcohol test, these results could help prove impairment.


Truck drivers cannot use controlled substances. This includes anything that is habit-forming, regardless if they have a prescription for it. Drivers cannot take any medication that adversely affects ability to drive in a safe manner. This is more difficult to prove. One possibility is if the driver had the prescription in the truck at the time of the accident.


Some truck accidents occur when the driver falls asleep at the wheel or is fatigued. Certain factors increase the risk, like driving at night and for several hours at a time. This type of impairment influences the driver’s ability to pay attention to the road and slows down reaction time.

Plaintiffs may present evidence of a violation of hours-of-services rules. Federal trucking laws limit the amount of time drivers may spend behind the wheel. If the driver’s logbook or electronic records show a violation, it may establish fatigue as a contributing factor.

An Attorney Can Help Assemble Evidence after a Truck Accident

In any accident, there are some basic types of evidence that can be essential to prove liability. The police report is one. It might include citations for impaired driving, or may indicate factors contributing to the accident, like a driver falling asleep behind the wheel. Accident victims can request a copy of the report from the police department that responded to the scene.

But some documents and records are in the hands of the trucking company. An attorney can draft a spoliation letter to preserve this evidence, and then request access to it.

Spoliation letters preserve:

  • personnel files;
  • alcohol/drug testing results; and
  • driver’s logbook, among other things.

Consult with Bressman Law after a truck accident for help gathering and presenting evidence to establish the truck driver’s impairment. Call 877-538-1116 or contact us online to set up a consultation with an attorney.