Reed Diamond

Former Homicide: Life on the Street star Reed Diamond has signed on to guest-star on The Mentalist, TVGuide.com has learned.

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Diamond will play Ray Haffner, a confident CBI supervising agent who runs a tight ship. As we previously reported, Haffner will lead a group of agents assisting Lisbon (Robin Tunney) and her team with the investigation of  a personal trainer's murder. Something tells us the CBI may not be big enough for both teams.

Diamond, 44, is best known for his work as Detective Mike Kellerman on Homicide. He has recurred on such shows as Judging Amy, Dollhouse, and 24, and he played the pivotal role of Detective Terry Crowley in The Shield's pilot. He currently stars on TNT's Franklin & Bash.

Check out photos of the Mentalist cast

Diamond is slated to appear in Episode 2 of The Mentalist's fourth season, which starts Thursday, Sept. 22 at 10/9c on CBS.