Probable cause to search means there is a fair probability that evidence of a crime will be found in the area police wish to search. Some issues that could give police probable cause to search your car might include: 1. Marijuana is in the car in an open container. 2. The police smell marijuana on drivers who are under the age of 21. 3. There is more than 1 oz. of marijuana in plain sight. 4. The police smell burnt marijuana, and you are showing signs of impairment that could indicate you are driving under the influence of marijuana.  Remember, while possessing small amounts of marijuana is lawful, driving while under the influence of marijuana is not lawful. If police have sufficient evidence that there is probable cause that a DUI is in progress, they may still search your car.