Marcos Costa, 46, is charged with murder, vehicular manslaughter and reckless driving in the 2009 crash. The crash killed Angel Posca and his 12-year-old daughter Angelina. A dozen others were injured.
Costa's attorney claims a combination of "insidious" geography and the lack of a runaway truck ramp on Angeles Crest Highway caused the crash in April 2009.
"In this case, there's no evidence that he committed a crime," said attorney Edward Murphy.
Murphy told jurors that Costa's truck and its brakes were working properly throughout the drive, until Costa reached the last mile-and-a-half of the highway.
"The horror of the situation as you're barreling down is that there is no way to stop the truck," Murphy said. "This is the reason for the accident. We know that Mr. Costa was in a panic, doing everything- including praying- to stop the truck. Do you think he wanted to hit anybody? Of course he didn't."
Prosecutors gave their closing arguments on Tuesday. They say Costa shouldn't have been on the highway in the first place. They contend he ignored several warnings, including an off-duty firefighter who told him to turn around because his brakes were smoking.
"No, this was not just an accident, not a case where everything was going fine," said Deputy District Attorney Carolina Lugo, telling jurors the truck was a "25-ton lethal weapon."
They dismissed Costa's claim that the crash was simply an accident, saying he should have taken more care with the rig.
Costa, who is Brazilian and speaks Portuguese, says language difficulties prevented him from understanding the warnings.
Lugo countered, however, that Costa still should have seen the smoke coming from his struggling brakes.
Jury deliberations will begin Thursday morning. If convicted on all counts, Costa faces life in prison with the possibility of parole.
City News Service contributed to this story