The more information an officer has, the better, so nothing should be discounted without first determining its veracity. Since drug-related cases comprise the majority of search warrants served, informants are the most prevalent source of information. Informants may provide reliable information, but they should never be counted on. Typically, the informant is a criminal himself, and his word should not be trusted. Any information from an informant should be checked before heading to a magistrate for a search warrant.
Patrol officers are an excellent source of information.
There should not be any reason to distrust a fellow officer, but the information should be confirmed regardless. Because they are familiar with a neighborhood and the people who live there, patrol officers can easily recognize suspicious activity. Chances are they have even been to the residence where drugs are being sold and can provide you with valuable information for the service of the search warrant. There are also times when a detective will initiate a search warrant. In some instances, you will not deal with a person directly.