Angel Posca, 58, and his 12-year-old daughter Angelina died in the accident in La Canada on April 1, 2009, and 12 others were injured.
The first person to take the stand in the trial was Yanette Posca, who lost her husband and her youngest child. She was on the stand for less than 10 minutes.
During her emotional testimony, Yanette Posca blamed trucker Marcos Costa for ignoring warnings about safety issues with his truck and losing control of the vehicle on Angeles Crest Highway.
She said she spoke with her daughter the day she died, but she didn't get to see her.
The attorney representing Costa asked if she understood that the verdict in the case had no bearing on her pending lawsuits against Costa and others, to which she replied, 'Yes."
Yanette Posca said she wanted to be in court every day and watch the proceedings.
"They're talking about my family that was taken from me. I feel this involves me. They took my family. My family is gone," she said on the stand.
Following Yanette Posca's testimony, Melissa Watkins testified. Watkins worked in the coffee shop that the truck crashed into.
"I looked up, and I only had time to say, 'Oh God,'" she said.
Watkins said she heard what sounded like thunder and saw the truck dragging the red car Angel and Angelina Posca were in.
"I saw toys in the streets. I saw that red car, and that's I think where we all just ... we knew that something was just extremely bad. I think that was the hardest thing," Watkins said.
Costa faces seven counts, including two counts of second-degree murder and two counts of vehicular murder. If convicted on all counts, Costa faces life in prison.