New Mexico prosecutors say 44-year-old Paul Othello Smalls was sentenced Monday by a federal judge in Las Cruces.
Smalls was convicted last November of retaliation against a witness or informant, tampering with a witness or informant and killing a person aiding a federal investigation.
Prosecutors say Smalls and two other men strangled 32-year-old Philip T. Gantz on Dec. 30, 2004.
Gantz was giving authorities information about the Roswell area's meth trade and was set to testify in a federal case.
Smalls was a county detention officer from 2002 to 2003. He was being held for raping and severely beating his wife at the time at Gantz's killing.