A retired police detective said he was shocked to hear rap mogul Marion "Suge" Knight had allegedly confessed to the murder of rapper Notorious BIG.
Notorious BIG was 24 when he was shot dead in 1997
Fred Miller told a US court it was one of several clues that linked the Death Row Records founder to the killing.
Mr Miller retired from the LA police in 1999 where he spent time probing BIG's death - real name Christopher Wallace.
A legal action for wrongful death is being brought by Wallace's family, who blame the police for his killing.
Wallace, who was also known as Biggie Smalls, was killed on a Los Angeles road in March 1997, after seven shots were fired into his vehicle.
His death came six months after the fatal shooting of rival rapper Tupac Shakur, who was signed by Mr Knight's Death Row Records.
Police closed an investigation into Wallace's death earlier this year, saying there was not enough evidence to prosecute.
Under questioning from Wallace family lawyer Robert Frank, Mr Miller told the court he had interviewed Mario Ha'mmond, a cellmate of Mr Knight's at a San Luis Obispo prison.
"I was rather shocked at what he told me," Mr Miller said.
"He told me he had spoken with an individual named Suge Knight and that Knight told him that he had had Biggie Smalls murdered."
He added that the alleged confession, along with gunshot residue found inside Mr Knight's Chevrolet sedan and a flurry of calls placed among Death Row associates in the two hours before the killing, all linked him to the murder.
But Mr Miller added he was unable to come up with any concrete connection between Mr Knight and the man he alleged to be the gunman, Amir Muhammad.
Wallace's family is attempting to prove through the courts allegations that former police officer David Mack used his police expertise or equipment to arrange for Mr Muhammad to kill him at Mr Knight's request.
The suit alleges the LAPD covered up Mr Mack's involvement in the killing and seeks damages from the city of Los Angeles.
But Mr Knight - who has unrelated convictions for assault and weapons - was never named an official suspect or arrested.
He has repeatedly denied any involvement in the killing and was not named in the suit.