LOS ANGELES -- Former Raiders defensive end Anthony Wayne Smith was found guilty Thursday of murdering three men, including two whose faces appeared to have been branded with a hot iron.

A Los Angeles County jury convicted the 48-year-old Smith of three counts of murder in the shooting of two brothers in 1999 and the stabbing of another man in 2001.

The jury found that all three had been kidnapped and tortured. It deadlocked on a fourth murder charge.

Former Raiders defensive end Anthony Wayne Smith was convicted Thursday of three counts of murder in the shooting of two brothers in 1999 and the stabbing of another man in 2001. USA TODAY Sports

Smith, who retired from the NFL in 1998, could face life in prison without the possibility of parole at his Dec. 21 sentencing.

Smith's attorney, Michael Evans, said his client maintains his innocence and will appeal the convictions.

Evidence at the 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, according to Deputy District Attorney Tom Trainor, who prosecuted the case

Also compelling, Trainor said, were books about killing techniques found in Smith's possession. The titles included "Kill Without Joy!", "Professional Killers: An Inside Look" and "The Outlaw's Bible."

No murder weapons were recovered, no DNA evidence was presented and prosecutors didn't address possible motives at trial.

Defense attorney Evans said the evidence connecting Smith to the killings was insufficient and parts of the investigation were improper.

Evans said he didn't understand why the jury found Smith guilty and that he was disappointed that jurors declined to explain their reasoning afterward. The judge in the case declined to compel the jurors to explain their verdicts, Evans said.

"My client's facing life without the possibility of parole here, and I think he deserves at least the benefit of that knowledge," Evans said.

In 2012, Smith was awaiting retrial on a murder charge in the 2008 death of Maurilio Ponce when he was charged with three additional cold-case killings.

They include the 1999 killing of Kevin and Ricky Nettles. The brothers were found shot to death and their bodies dumped about eight miles apart after they were kidnapped from a Los Angeles car wash. Both had U-shaped branding burns on their cheeks, and Ricky Nettles also had numerous burns across his abdomen and feet, according to evidence presented at trial.

Smith also was convicted the June 2001 killing of Dennis Henderson, who was kidnapped in Los Angeles with another man by several gunmen. The other man was released, but Henderson was found stabbed to death in a rental car, his body covered in more than 40 non-fatal stab wounds inflicted before his throat was slashed, according to evidence presented at trial.

The jury deadlocked in the killing of Ponce, a friend of Smith. Prosecutors had argued that Smith lured Ponce to an Antelope Valley desert highway where the mechanic was beaten, stomped and shot over a business deal gone wrong.

Smith was drafted as a pass-rusher 11th overall by the Los Angeles Raiders in 1990. He amassed 57½ sacks and 190 tackles before retiring in 1998, after the team returned to Oakland.