Just had a thought regarding warentless searches of cars...
The automobile search doctrine allows cars to be searched without a warrant so long as there is probable cause and the car is "readily mobile". So if a cop says he is going to search your car, or you think he is about to, and you have something illegal, just slash your tires. Now it is no longer readily mobile and any warentless search would be illegal.
@AncientGood Oh shit I just learned the supreme court (specifically the PA jurisdiction) they can no longer search your car off of just probable cause.. the automobile doctrine was over turned. So now your car has the same protection as your home (almost), in other words they need exigent circumstances to search NOT just probable cause. Otherwise they can get a search warrant.