Modifications for DUI law yet again! The never ending adjustment to Tennessee DUI law. A person who has a Blood Alcohol Content (BAC) over .15 is required to have an interlock device on the vehicle if convicted. Also, if you have previously been convicted of a DUI, the police can perform a forced blood draw to test a person’s (BAC). If a person has a passenger under 16 years old in the car, the officer can also compel a blood draw if they believe the person is impaired.