They said Smith posed as a police officer to kidnap brothers Ricky and Kevin Nettles from their Los Angeles car wash business on Nov. 10, 1999 before killing them.
Smith was also accused of kidnapping Dennis Henderson on June 24, 2001, from the Mar Vista section of Los Angeles before beating and stabbing him to death.
Prosecutors said Ponce was lured to an Antelope Valley desert highway in 2008 where he was beaten and shot after a business deal went bad.
No motives were given for the other killings.
The Nettles brothers’ bodies were found about eight miles apart. Both had U-shaped branding burns on their cheeks, and Ricky Nettles had numerous burns across his abdomen and feet.
Prosecutors said Henderson’s body was found in a rental car and had more than 40 non-fatal stab wounds inflicted before his throat was slashed.
Evidence at Smith’s trial included two identifications by witnesses, zip ties found on one of the victim’s hands that came from the same production batch as ties in Smith’s possession, and rope found on one body that was similar to rope also in Smith’s possession.
Prosecutors said books on how to kill people were found in Smith’s possession. The titles included "Kill Without Joy!" and `’Professional Killers: An Inside Look."
Smith was drafted as a pass rusher 11th overall by the Raiders in 1990 while the team played in Los Angeles. He amassed 57 1/2 sacks and 190 tackles before retiring after the 1997 season, by which time the team had returned to Oakland.