In determining whether reasonable cause exists to justify an arrest, a law enforcement officer may take into account all facts and circumstances, including those based upon any expert knowledge or experience which the officer in fact possessed, which a prudent officer would judge relevant to the likelihood that a crime has been committed and that the person to be arrested has committed it, and for such purpose the officer may rely on information he receives from any informant whom it is reasonable under the circumstances to credit, whether or not at the time of making the arrest the officer knows the informant’s identity.