One of the first things we tell clients in our criminal defense practice is never give a law enforcement officer permission to search anything. The Constitution places strict limits on when law enforcement can perform a search, and oftentimes officers won't have a warrant or the probable cause they require when they want to search a suspect's property. However, the moment that a suspect consents to a police officer's search, most of that suspect's constitutional protections disappear. For this reason, "consensual encounters" are one of the most popular techniques that officers use to collect evidence. When an officer asks if he can search a vehicle, he usually is not just being polite, but likely has doubts about whether the constitution allows him to perform a search without the suspect's permission.