After stealing the vehicle of a civilian (if you steal a vehicle from a police officer or near an officer, this trick will not work) you simply need to follow that person for about 5-10 seconds to see if they bring up a phone or mention the police. If they do not, leave that person be and don't waste your time. However, if they do in fact mention the police or pick up their phone, all you need to do is simply spook them or "slightly" run them over. Following this trick, an encounter with the annoying police can be avoided, saving invaluable time!