When first applying for a driver’s license, you must also agree to submit to chemical testing if you are suspected of drunk or impaired driving by a law enforcement officer. State-administered chemical testing is a forensic analysis of your breath, blood or urine to determine blood alcohol level or the presence of drugs.
Each state has an implied consent law and it can vary from state to state. Typically, the implied consent law says that once a driver is operating a vehicle, the driver has “implied” that they will provide their license and proof of insurance, perform field sobriety tests and submit to chemical testing if requested by a police officer.
A driver can refuse the chemical tests, but there are penalties. You can still be arrested for DUI even if you refuse to perform any field sobriety evaluations or chemical testing. If an officer believes you are impaired, you can be charged with “less safe” DUI. In some states, the prosecution can use your refusal against you in a DUI-DWI trial.