A DWI case only goes to trial if a person pleads not guilty. Then the trial process begins with jury selection.
Every DWI case is different, but there are some forms of evidence used in most cases.
Test results
Officers use two types of tests to determine a person’s intoxication level: chemical tests and field sobriety tests. Chemical tests determine the blood alcohol level using blood, urine, or breath. Anything higher than .08 looks bad to a jury, but the officer must prove that he or she obtained the sample properly.
Officers conduct field sobriety tests at the time of the arrest. These are just actions the officer asks the driver to do to test balance and coordination.
Officer testimony
When officers make arrests, they submit reports that detail their accounts of it. They then testify in court and explain the decision to pull someone over and to then arrest that driver.
Video evidence
Video evidence usually comes in the form of dashboard cameras that record from the dashboard of the police vehicle and body cameras that record from the officer’s body. Sometimes people watching the arrest take place may record it as well.
Your statements
What the arrested driver says matters as well. Video of the driver admitting to anything illegal may enter evidence, but if there is no video, the officer may testify to hearing the driver say it.
Eyewitness testimony sometimes lands in evidence, and in cases involving illegal substances, drug recognition experts may testify to seeing signs of drug use. All evidence is contestable.