Smith, 45, is charged with murder, kidnapping and special circumstances in the deaths of brothers Ricky and Kevin Nettles, ages unavailable, in November 1999 and Dennis Henderson, 33, in 2001, the Los Angeles Times reported Sunday.
A motive for the slayings was unclear.
Prosecutors have also brought new charges against Smith in the death of Maurilio Ponce, 31, of Lancaster, whose body was found three years ago. A judge declared a mistrial earlier this year on charges Smith killed Ponce. Two other men also were charged in Ponce's death.
All of the men except Ponce were found branded with hot tools, prosecutors said.
During the preliminary hearing, several prosecution witnesses described how the Nettles brothers, who operated a mechanic's shop, were abducted and later found dead with duct tape around their heads.
Smith, who played defensive end for the Oakland and Los Angeles Raiders between 1991 and 1998, has pleaded not guilty to all the charges.
Los Angeles County prosecutors still must decide whether to seek the death penalty.