Yes, police can detect jammers. There are a few ways that they can do this. One way is through the use of a radio frequency detector. This type of detector can be used to find out if there is any interference with the radio waves that are being used by the police for communication. Another way that police can detect jammers is through the use of a GPS tracking device. If a jammer is being used, it will block the GPS signal and the police will be able to track the location of thejammer.