Tactical Crime Analysis: Research and Investigation - Paperbackby Derek J. Paulsen (Author), Sean Bair (Author), Dan Helms (Author) Research has shown that the majority of crimes are committed by persistent or serial offenders, with as little as seven percent of offenders accounting for approximately 60 percent of all crimes. By focusing police efforts on these prolific offenders and learning to identify, analyze, and resolve the crimes they commit, the law enforcement community can protect and defend the public