Truck driver Marcos Costa, 44, of Massachusetts, is charged with two counts each of murder and vehicular manslaughter and three felony counts of reckless driving.
The Los Angeles County district attorney's office says Costa ignored weight restrictions on Angeles Crest Highway, causing the brakes on his big rig to fail as he came down the mountain.
His vehicle crashed into four vehicles and a bookstore at the intersection of Angeles Crest Highway and Foothill Boulevard.
Costa has pleaded not guilty to the charges. If convicted he could be sentenced up to life in prison with the possibility of parole.
City News Service contributed to this report.