Probable cause means that the officer has articulable facts coupled with a reasonable belief that you have consumed alcohol or drugs and are too impaired to drive. That means the officer cannot just think you might have had a few drinks. You must also display physical signs of impairment, such as: Weaving across lanes Sudden braking or accelerating for no reason Swerving into oncoming lanes Running traffic signals Slurred speech or impaired speech patterns Odor of alcohol or marijuana Loss of physical dexterity (stumbling, falling, dropping objects). None of these things proves you are intoxicated. Only a blood test can definitively prove you have been drinking or using drugs. These things only establish that there are sufficient grounds for a blood or breath test.