After a five-week Solano County Superior Court trial and three days of deliberations, a jury on Tuesday found the Quintanilla siblings guilty of respective charges related to the Oct. 30, 2021, gunshot slaying of a 19-year-old woman in Fairfield.

Seated at the defense table in Department 11, Jessica Yesenia Quintanilla, 24, of Pittsburg, held her head in her hands, her long black hair hiding her face, as the court clerk pronounced that she was guilty of the first-degree murder of Leilani Marie Beauchamp of Carmel.

Her defense attorney, William Alan Welch of San Francisco, also began to hold his head in his hands as the court clerk continued to enumerate several enhancements the jury of seven women and five men found to be true: that Jessica Quintanilla used a gun, fired it and did the shooting.

Welch asked for a polling of the jury, and the verdict was unanimous.

Turning to her brother, Marco Antonio Quintanilla, 30, also of Pittsburg, the court clerk indicated the jury found him guilty of being an accessory after the fact and possessing a firearm after being convicted of a prior violent felony.

His attorney, Laurie D. Savill of San Francisco, also requested a polling of jurors, and the verdict was unanimous.

Judge William J. Pendergast thanked the jurors for their service. Then, after conferring with Deputy District Attorney Ilana Shapiro and the defense attorneys, he set a court trial at 9:30 a.m. Dec. 20 to rule on aggravating factors and prior convictions. (A court trial, as opposed to a jury trial, occurs when a judge listens to the evidence and decides the case without a jury.)

Marco Antonio Quintanilla, 30, of Pittsburg, in Department 11 of Solano County Superior Court during his November 2021 arraignment, was found guilty of being an accessory after the fact. (Joel Rosenbaum / Reporter File Photo)

A sentencing date remains pending for the Quintanillas and will not occur until the court receives presentencing reports and, for Marco Quintanilla, a report from the Solano County Probation Department.

Responding to a question from the judge, Shapiro requested that Marco Quintanilla, out on bail as the case progressed over the years, be taken into custody. Savill asked the Pendergast to allow her client, the father of one, to remain free until sentencing.

The judge, citing Marco Antonio’s felony conviction, ordered him jailed and he was booked into Solano County Jail without bail shortly after 3 p.m. Tuesday.

Jessica Quintanilla, the mother of two, ages 7 and 4, continues to be jailed without bail.

She was found guilty of shooting Beauchamp (pronounced “BEECH-um” during the trial) on the morning of Oct. 30 while she was lying in bed with Juan Parra-Peralta, an airman stationed at Travis Air Force Base, with whom Quintanilla once had a romantic relationship.

During the trial, Shapiro recounted that Jessica Quintanilla entered the second-floor bedroom of a Cascade Lane home that Parra-Peralta rented. She was there to retrieve some of her personal effects and, according to her testimony, did not know Beauchamp was there.

Quintanilla testified she argued with Parra-Peralta but denied she was screaming, as Shapiro argued, adding that she was “loud.”

Shapiro repeatedly pressed Quintanilla about her memory of what happened just before a single bullet entered and exited the right side of Beauchamp’s head, killing her.

Beauchamp, said Shapiro, was naked in bed, vulnerable, did not have a weapon, and was not threatening, a statement Quintanilla agreed with.

But boring in on Quintanilla’s possible state of mind, Shapiro asserted that Quintanilla was angry at seeing Parra-Peralta, 21 at the time, with a woman she told him “not to hang around with” and not to post anything on social media about Beauchamp. The prosecutor showed Quintanilla printed copies of text threads on social media.

Shapiro asserted that Quintanilla told Parra-Peralta not to take Beauchamp to a mid-October sideshow, a demonstration of automotive stunts, often in a street intersection.

But Quintanilla denied ever saying not to go with Beauchamp.

While on the witness stand, Quintanilla admitted that both she and Parra-Peralta possessed firearms, Glock semi-automatic handguns, at that time, but the guns remained in Parra-Peralta’s custody.

Jessica Quintanilla testified that they were “ghost guns,” firearms made from parts purchased online and not federally licensed or traceable.

Leilani Marie Beauchamp, 19, of Carmel (Courtesy photo/Monica Beauchamp)

After killing Beauchamp, Jessica Quintanilla, threatening him with her handgun, forced Parra-Peralta to drive to a rural road near Salinas, where Parra-Peralta dumped Beauchamp’s blanket-wrapped body down a hillside and into vegetation.

Parra-Peralta later led Monterey County Sheriff’s Office investigators to the Beauchamp’s body on Nov. 1.

He, along with fellow airman Damien Ponders, both of whom were later discharged from the Air Force under less-than-honorable conditions, were granted immunity in exchange for their testimony.