William Daniel Cady, 26, wiped tears from his eyes as the jury's verdict was announced after a day of deliberations.
Sentencing is scheduled for July 10.
Deputy District Attorney Makenzie Harvey told jurors in her closing argument that Cady was warned by a judge three years before the Jan. 10, 2014, crash about the dangers of alcohol.
The defendant "thumbed his nose" at the judge, his parents, and friends who told him not to drink and drive, the prosecutor said. Cady told them, "You guys don't need to tell me what I already know," according to Harvey.
The prosecutor was referring to Superior Court Judge Melinda Lasater telling the defendant in 2011 to abstain from alcohol following a vandalism conviction in which he punched through a wall.
"You can't afford to have alcohol in your life," the judge told Cady then. "You're not to consume alcohol."
While Cady was on probation in the vandalism case, he totaled his Mustang in 2012 after drinking and driving too fast and crashing on a curved road, Harvey told the jury.
The prosecutor said the defendant made a number or choices the night of the fatal crash to drink and drive.
Cady's blood-alcohol content was somewhere between .10 and .18 percent at the time of the crash, which happened about 11:15 p.m., Harvey said.
She said Cady's consumption of alcohol and marijuana, also with his reckless, aggressive attitude, made for a "deadly combination" that night.
Harvey said the defendant was in a unique situation because he knew and had been warned about the dangers of drinking and driving.
One of Cady's passengers, Trevor Rodgers, testified that Cady was going too fast and sped up and laughed when all five passengers asked him to slow down just before he lost control of his SUV going an estimated 87-97 mph on the transition ramp from northbound Interstate 805 to westbound state Route 52.
"It must have felt nothing short of terrifying," the prosecutor said.
Harvey said the SUV flipped at least five times, and four passengers were ejected from the vehicle.
Taylor Bednarski, 29, and Shon Gilliam, 23, died at the scene. A third passenger, 35-year-old Jeffery Becker of Kern County, died in the crumpled SUV.
According to testimony, Cady and his five companions were drinking at one of their homes, then at the Sky Box sports bar in Clairemont in the hours before the crash.
After leaving Sky Box, one of the men bought whisky at a grocery store, then the group made its way to a second bar and were kicked out of that establishment for being too rowdy, according to testimony.
A bartender testified that the group of men were "all visibly wasted" an hour before the accident. Camilly Berardi said she offered to call a cab or car service to take Cady and his five friends home because she didn't want them on the road.
Cady's attorney, Rick Layon, told the jury that his client was guilty of gross vehicular manslaughter and DUI, but not guilty of murder.
Layon urged jurors to disregard testimony from Berardi and an officer who interviewed the surviving victims following the crash, saying they weren't credible.
Layon said Lasater's admonishment to Cady in 2011 did not put the defendant on notice about the dangers of drinking and driving.
In order to find Cady guilty of second-degree murder, jurors would have to find that the defendant didn't care what happened the night of the accident, Layon said.