A mistrial was declared after a Sacramento jury on Friday deadlocked in its decision of the death penalty for Adel Ramos, who killed Sacramento police Officer Tara O’Sullivan in a 2019 ambush that shocked the capital region.

In Sacramento Superior Court, the jury told Judge James Arguelles that it was split 11-1 on imposing capital punishment on Ramos, 51, despite the state moratorium on death sentences.

Arguelles then declared the mistrial, ending a monthlong trial in which prosecutors tried to convince the five men and seven women that Ramos should be put to death.

California has not carried out an execution since 2006, and a moratorium on capital punishment has been in place since shortly after O’Sullivan’s murder. But the death penalty remains on the books, and prosecutors say a future governor could reverse the moratorium and re-open the state’s shuttered execution chamber. More than 600 inmates are under a sentence of death in California, the most in any state.

Ramos pleaded guilty on Aug. 30 to felony counts including murder with special circumstances for O’Sullivan’s slaying and attempted murder of another officer at the violent, bloody scene in Del Paso Heights.

O’Sullivan, 26, who had graduated six months earlier from the Sacramento Police Department’s academy, was showered with bullets by Ramos on June 19, 2019, as she attempted to help a woman retrieve her belongings from a home where he had been behaving erratically. She was mortally wounded and lay on the ground nearly an hour before tactical officers were able to secure her rescue. After an hourslong standoff, Ramos surrendered.

Ramos initially pleaded not guilty, but the trial was delayed as his attorneys argued that he was not mentally competent to stand trial.

O’Sullivan’s murder sent shockwaves through the capital region, and led the city to rename the H Street Bridge over the American River among memorials.

Prosecutor Jeffrey Hightower told jurors that O’Sullivan, who grew up in the Bay Area and graduated from a criminal justice program at Sacramento State, was a devoted young officer who even as a child displayed a keen sense of right and wrong. She was still in training when she urged her partner to respond to a call from Megan Jansa, who at the time lived with Ramos in the Redwood Avenue home she had inherited from her grandfather.

Jansa had left the home amid threatening behavior by Ramos, and O’Sullivan and her partner and training officer Daniel Chipp decided to accompany her there to retrieve some clothing and her dogs. Ramos, Hightower said, was hiding at the residence behind a series of “murder holes” he had drilled into the walls of the house, enabling him to shoot at the officers while obscuring his location.

The officers searched the property to see if anyone was there. Ramos did not respond to their calls, and Chipp even told other officers via radio that the house might be empty. But suddenly he began shooting, striking O’Sullivan and shouting epithets at her as she lay on the ground, bleeding.

He held the rest of the officers at bay for hours, shooting in several directions from his hiding place, making it impossible for them to rescue her.

His lawyers argued that mental illness and a violent and unstable childhood should be considered mitigating factors in the case, and asked jurors not to sentence Ramos to die.

California has spent $313 million on death penalty prosecutions and appeals in the five years since Newsom imposed a moratorium on executions, an analysis showed. The state has dismantled the execution chamber at San Quentin and moved nearly all of the inmates out of the old death row.

But prosecutors continue to seek capital punishment in the state, saying it sends a message to defendants.