LOS ANGELES, CA – A Costa Mesa woman has been convicted of multiple felony charges stemming from a 2022 hit-and-run crash that killed a 60-year-old man as he and his wife were crossing a street in Laguna Beach after celebrating their wedding anniversary.
Sysillia Kianna Morrison Montes De Oca, 22, was found guilty by a jury on Sept. 10 of gross vehicular manslaughter, hit-and-run with permanent and serious injury, and failing to stop at a hit-and-run involving injury or death. Jurors also found true a sentencing enhancement for fleeing the scene of a vehicular manslaughter.
Her sentencing hearing is scheduled for Nov. 13.
The case dates to Aug. 11, 2022, when Stanley Isaacs, 60, and his wife, Catherina, were crossing South Coast Highway at Pearl Street in a marked and illuminated crosswalk. The couple, both residents of Costa Mesa, had been in Laguna Beach to celebrate their anniversary.
According to the Laguna Beach Police Department, officers responded to the collision at about 9:38 p.m. after the couple was struck by a vehicle. Both victims were transported to a local hospital. Isaacs later died from his injuries, while his wife was treated for injuries and released.
Fatal collision and investigation
Police identified the vehicle involved as a Volkswagen Jetta. Investigators subsequently located a silver 2009 Jetta concealed inside a garage in Aliso Viejo and impounded the vehicle as evidence.
Authorities identified Morrison Montes De Oca as the driver during the investigation. She surrendered to Laguna Beach police on Aug. 12, 2022, and was arrested on suspicion of vehicular manslaughter with gross negligence and felony hit-and-run. At the time, she was 18 years old.
The original police investigation also identified speed as a possible contributing factor. Police said investigators were examining whether drugs or alcohol played a role in the collision.
Information reviewed by Street People indicates that the case remained active for years before reaching a jury verdict this month. The conviction now establishes the outcome of the criminal trial, although the sentencing phase has not yet occurred.
During closing arguments, Deputy District Attorney Justin Kim told jurors that Morrison Montes De Oca had told three other passengers in the vehicle that she planned to speed up shortly before the collision. Prosecutors also argued that the couple was nearly across the roadway when they were struck.
Kim described the injuries suffered by Isaacs during the impact, including an “internal decapitation,” a skull fracture, a snapped spine and severe rib injuries. Prosecutors said the collision sent Isaacs through the air before he landed on the roadway.
The prosecution’s account was disputed by defense attorney Mike Molfetta, who challenged evidence presented about the vehicle’s speed and argued that the collision should not be treated as proof of gross negligence. The defense also argued that Morrison Montes De Oca had only recently begun driving at the time of the crash and that she left the scene after panicking and being urged to do so by passengers.
The defense additionally challenged the prosecution’s account concerning marijuana use, arguing that there was no evidence she had been smoking marijuana inside the vehicle immediately before the collision.
Vehicle located after crash
The investigation moved quickly in the days following the crash. Laguna Beach police said members of the public helped investigators identify the driver after authorities released information seeking the vehicle involved.
Detectives then located the Jetta in an Aliso Viejo garage. The vehicle was taken into evidence as investigators worked to establish who had been driving when the couple was struck.
The department announced the arrest the day after the collision, saying Montes De Oca had surrendered at approximately 6 p.m. She was booked and later released after posting the statutorily set $100,000 bail.
The case later expanded beyond the driver. Court records cited in recent reporting show that Jack Francis Bannigan pleaded guilty in July 2026 to being an accessory after the fact for his role in concealing the damaged vehicle. He received one year of informal probation and was ordered to complete 120 hours of community service.
The circumstances surrounding the vehicle’s concealment became part of the broader case as prosecutors presented their account of what happened after the collision.
Conviction follows four-year-old crash
More than four years after the fatal crash, the jury returned guilty verdicts on all three felony counts against Morrison Montes De Oca.
The conviction for gross vehicular manslaughter concerns Isaacs’ death, while the hit-and-run-related charges address the circumstances surrounding the collision and the decision to leave the scene.
The jury also found true the sentencing enhancement alleging that she fled the scene of a vehicular manslaughter.
No sentence has yet been imposed. The Nov. 13 hearing will determine the next stage of the criminal case.
The conviction comes after a trial in which prosecutors and the defense presented sharply different interpretations of the events leading up to and immediately following the crash. The defense maintained that the collision was not sufficient to establish gross negligence beyond a reasonable doubt, while prosecutors argued that the driver’s conduct before and after the impact supported the felony charges.
For the Isaacs family, the case stems from a night that had begun as an anniversary celebration before ending in a fatal collision.
The Laguna Beach Police Department said it continues to extend its condolences to the Isaacs family and credited investigators, officers, prosecutors and members of the community who contributed to the case.
The criminal case remains active pending Morrison Montes De Oca’s sentencing hearing in November.
