Three inmates were convicted of first-degree murder Tuesday in a 1998 Los Angeles jailhouse killing that authorities believe was a hit ordered by the Mexican Mafia.

Christian Knighten, Frankie Lujan and Dennis Ray Morris were convicted of killing Robert Tiernan, 32, while Tiernan and the defendants were locked up at the Men’s Central Jail.

The three defendants were also found guilty, along with inmate Red Culbertson, of conspiracy to commit murder. Culbertson was acquitted of the first-degree murder charge.

According to Deputy Dist. Atty. Tom Rubinson, Tiernan was stabbed 19 times and had a “massive crush wound to his head.”


He was killed in a cell and his body was moved to a shower, where sheriff’s deputies found him.

Tiernan was in jail facing charges of possession of a controlled substance and a parole violation.

Rubinson said that the defendants, who shared a prison cell where Tiernan’s blood was found, carried out an order by the Mexican Mafia to discipline Tiernan.