The courtroom was cleared as paramedics were called to the scene.
The jury deliberated for one day before reaching the guilty verdict. Judge Robert J. Perry remanded Johnson into custody. She was handcuffed to a gurney and taken out of the courtroom.
"There was probably a lot of things going through her mind. She has a daughter, her only child, so I know she's going to miss her," said Randy Brown, a friend of the victim. "And then what she did. Bad things in your life, you never can forget them."
Johnson, 32, was on trial for first-degree murder for fatally shooting her husband Marcus Lemons in Compton in February 2009. She was a CHP officer at the time.
Johnson had reported the shooting, but said she shot him in self-defense after he became physically abusive during an argument.
Detectives doubted her story and arrested her last January. Prosecutors said Johnson shot Lemons near a 91 Freeway off-ramp, then drove to her parents' home in Compton with her husband's body in the passenger seat.
"I feel justice was served," Brown said. He had known Lemons for 10 years. They owned a barber shop together in Compton.
Johnson faces 50 years to life in prison when she is sentenced on March 9.