A person who has been charged with a DUI/DWI criminal offense will face a jury trial or a bench trial (trial before the judge) unless the defendant makes a plea bargain with the government/prosecution. Laws and procedures vary from state to state but a DUI/DWI charge is usually a misdemeanor offense—unless there are aggravating circumstances that may make it a felony—such as (1) having a child in the vehicle, (2) causing an accident that results in serious bodily injury or death, (3) having a blood alcohol concentration (BAC) that is significantly higher than the legal limit, (4) being charged within 10 years of a previous conviction, or (5) being charged with a second or third DUI/DWI offense.
At trial the government/prosecution will have the burden to prove beyond a reasonable doubt that the defendant was under the influence of alcohol or drugs or was intoxicated by alcohol or drugs, as provided by applicable law. The government/prosecution will generally introduce evidence of any chemical tests (blood, breath, or urine) and the testimony of the arresting police officer who interacted with the defendant and administered any field sobriety tests.
The defendant has no obligation to testify or put on any evidence at trial but may choose to do so to explain any relevant facts and circumstances that may constitute a defense to the charges or may mitigate the severity of the criminal offense.