When a driver is under the influence of alcohol, has a blood alcohol concentration level (BAC) of .08% or more, and/or is under the influence of any controlled dangerous substance, they can be charged with a DUI/DWI. A police officer who needs to determine sobriety will need probable cause to arrest for DUI/DWI and also to request a person submit to a chemical test.
The police can use a blood, breath, or urine test to scientifically measure the levels of alcohol or a controlled dangerous substance in your body. How police determine sobriety of a driver may be a field sobriety test. These tests are often used, but scientific evidence is vital for DUI/DWI convictions.