A former Los Angeles County Jail cellmate of Horace Burns, the convicted killer of four relatives of former football star Kermit Alexander, testified that Burns offered him $15,000 to kill the prosecutor and two witnesses in the case. Philip Lowden, a convicted robber, also said Burns, 20, offered him additional money to kill several of the jurors who convicted him. Testifying in the penalty phase of Burns’ trial, Lowden said he turned Burns down and decided to tell authorities of the offer to kill Deputy Dist. Atty. Sterling Norris, witnesses Ida Moore and Lisa Brown and several jurors. Burns faces the death penalty or life in prison without parole. Two other suspects in the murders will be tried later.