He can't speak, said defense attorney Denise Porter. So, Walker nodded to show the judge he understood what was happening.
The appearance was brief, just long enough for attorneys to ask for another court date.
Walker, 34, is charged with first-degree felony aggravated murder for Sgt. Derek Johnson's death on Sept. 1. Prosecutors have said that seeking the death penalty for Walker is a possibility.
Porter, who told 3rd District Judge Mark Kouris that she had not received a complete record of the case from prosecutors, did not comment to the crowd of reporters and television cameras outside the courtroom.
Walker also faces charges of attempted homicide for allegedly trying to kill Vaillancourt during the same shooting episode, and three counts of discharge of a firearm and one count of possession of a weapon by a restricted person, all third-degree felonies.
Vaillancourt, 34, also appeared in court Tuesday.
Though the two defendants were brought before the same judge, they were transported to their appearances separately and kept apart while at the courthouse.
Vaillancourt's attorneys said it's important to keep them apart for legal and personal reasons.
"There are a lot of emotions there," said defense attorney Matthew Kober. "These two have a long history together. But they're on different sides of the table in this case."
Kober noted they are optimistic about working out a plea agreement with prosecutors, or having the charges against Vaillancourt dropped.
She is charged with two counts of second-degree felony obstruction of justice for allegedly lying to investigators about what happened on the day Walker shot her and the Draper sergeant.
The woman, who was hospitalized for nearly a week after the Sept. 1 shooting and had been in a wheelchair, appeared Tuesday with her left arm in a sling. She still has pains where the bullet struck her, Kober said, but she's come a long way.
As she was led into the courtroom, Vaillancourt smiled at her attorneys and the judge. She wore a blue jumpsuit and swung her long, wavy hair behind her as she walked.
Her sister was also present in the courtroom, but declined to comment.
According to charging documents, Johnson, 32, was in a marked Draper City police vehicle at about 6 a.m. on Sept. 1, when he stopped at 13200 South Fort Street and noticed Walker standing outside his Volvo.
Authorities said Walker had stopped the car because he ran out of gas and the passenger-side front tire had gone flat from driving over a curb, a stop sign, a large rock and then through at fence at 13800 S. 933 East, court records show. He then continued driving a few blocks away to the area of 13200 South, police said.
When Johnson pulled up near the Volvo to see if he could help, Walker allegedly shot Johnson through the open front passenger side window of Johnson's police vehicle.
Johnson was struck in the chest by the bullet and tried to drive away northbound. Walker, who was allegedly under the influence of methamphetamine at the time, fired at least three more shots, which struck Johnson's marked vehicle, court documents state.
Johnson used his police radio to call "shots fired," but then lost control of his vehicle and crashed into a wooded area about two blocks north of where he was shot.
The medical examiner later determined Johnson died from a gunshot wound to the chest.
Salt Lake County District Attorneys Sim Gill has said Johnson was wearing a bulletproof vest, but the bullet struck in an area the vest did not cover.
Walker who shot himself in the face that day was hospitalized for his injuries before being booked into the Salt Lake County jail, where he remains in lieu of $2 million cash-only bail.
Vaillancourt, who also was treated at a hospital, is being held at the jail on $500,000 cash-only bail.
Both defendants are scheduled to appear again before Kouris on Dec. 3 for a status hearing.