Most radar detectors are undetectable. However, police may suspect a driver is using a radar detector if they observe the driver exhibiting erratic or suspicious behavior, such as slowing down significantly when they encounter a police car. Additionally, some radar detectors emit a signal that is detectable by certain types of police radar guns, which can alert the police to the presence of a radar detector. To avoid detection, it is recommended to keep the radar detector hidden and to use it responsibly while driving.