A big part of what law enforcement officers and do to help keep the public safe involves investigating potential crimes and gathering evidence so that prosecutors can bring charges against someone who violates the law. 

When it comes to driving while intoxicated (DWI) charges, knowing what evidence the police involved in a traffic stop will gather and later present to the court can help you make decisions about how to best defend yourself.

Police will typically testify about your driving and behavior

When officers want to prove that someone has committed an impaired driving offense, unless they were conducting a sobriety checkpoint, they have to have a justification for conducting the initial traffic stop. 

Generally, officers will point to certain driving behaviors, such as erratic braking, drifting across lanes, going the wrong way on a street or not turning on headlights or turn signals to establish why they initiated the traffic stop. They will then refer to certain behaviors during the stop, such as slurred speech, as justification for performing a field sobriety test.

Police will provide the results of field sobriety testing

Officers can have drivers perform a number of tasks, ranging from following the moving finger from side-to-side to walking in a straight line and turning. The performance of an individual in any of these tests can be part of the evidence used against them in court and justification for requesting chemical testing.

Police will provide chemical testing evidence if they have it available

Officers typically perform chemical breath tests during DWI stops, but it is also possible for law enforcement officers to conduct other chemical testing after an arrest, such as a blood draw or urine tests, though these require consent or a warrant. The results of the chemical test will help the state build a case for DWI. 

While that may seem like a lot of evidence, anything from an officer’s personal biases, possibly due to previous interactions with an individual, too medical conditions can impact the accuracy of an officer’s presumptions and the tests performed to establish impairment. In other words, it is possible to fight back despite the evidence.