U.S. District Judge Richard A. Snell said Manson follower Charles "Tex" Watson waived his right to attorney-client privilege when he let his lawyer sell the tapes to an author who wrote a book about Watson, the Los Angeles Times reported Wednesday.
Watson is serving a life sentence for the 1969 killing of actress Sharon Tate and four others by Charles Manson and his followers.
Los Angeles police want the taped conversations because they suspect Watson "may have discussed additional unsolved murders committed by followers of Charles Manson" on them.
Snell's ruling affirms an earlier decision by a bankruptcy judge that the LAPD can have the tapes of Watson and his attorney Bill Boyd who died in 2009.
LAPD will send detectives to Texas to pick up the tapes once Watson's 30 days to appeal the decision expire.