Green’s Dictionary of Slang

(US Und.) a note attached to an individual’s police record stating that they have been suspected (but not charged due to lack of proof) of committing a crime; the note requests that they be punished to the maximum extent for such lesser charges that can be brought.

1971		Oakland Trib. (CA) 6 June 26-EN/5: These ‘silent beefs’ are often the real basis of the parolee’s return to prison.
1973		Fresno Bee Republican (CA) 25 Nov. 88/5: Inmates [...] say the Board of Terms and Paroles has taken over the role of judge and jury when it refuses to grant paroles on the baiss of ‘silwent beefs’, or criminal charges in an inmate’s file.
1990		S. Morgan Homeboy 140: Silent beef. When the authorities believe the man guilty of a crime [...] which they cant prove and must settle for a conviction on a lesser charge, they attach memoranda to a man’s record stipulating the uncharged offenses. These memoranda ensure he is punished to the fullest legal limit of the lesser offense.