The jury, after brief deliberations on Tuesday, convicted Stacey Lonnberg, 52, of two counts of murder and one count of child endangerment, Deputy District Attorney Matthew Braker said.
A sentencing hearing for Lonnberg is set for Oct. 11 in Santa Clara County Superior Court in San Jose. She is facing a prison term of 36 years to life, Braker said.
The two-week trial wrapped up on Tuesday afternoon following closing arguments, and the jury reached its verdict that same day, Braker said.
The panel convicted Lonnberg in the deaths of her husband Frederic Lonnberg, 57, a UPS driver, and her daughter Tiffiny Gillette, 26, a hair stylist.
The crash happened at about 3:45 p.m. on Jan. 14, 2012, while Lonnberg drove north on state Highway 85 near Winchester Boulevard in a 2002 Toyota Tacoma pickup truck after drinking seven to eight vodka drinks and ingesting the pain medication oxycodone, Braker said.
Her husband, daughter and her daughter's 1-year-old son were inside the truck, he said.
The group had left Gilroy to attend a wedding reception for a friend in Belmont. Witnesses later told authorities that Lonnberg was driving at more than 80 mph and weaving through traffic, Braker said.
The Toyota hit another pickup truck, careened across other lanes and then flipped over six times, he said.
Gillette was thrown from the Toyota and died on the highway. Frederic Lonnberg died later at a hospital after he was partially ejected during the rollover crash.
Stacey Lonnberg and her grandson suffered only minor injuries.
An expert witness for the prosecution testified at the trial that Lonnberg's blood-alcohol level at the time of the accident was about .20, more than twice the legal limit for drunkenness, Braker said.
Defense attorney Javier Rios on Tuesday admitted to the jury that Lonnberg was an alcoholic, and was drunk and had taken pain medicine prior to driving the day of the accident.
Rios tried to convince the jury that the prosecution had failed to prove that Lonnberg was guilty of second-degree murder because she never had the intention of killing her husband and daughter.