A judge declared a mistrial Monday after jurors said they were at an impasse in the murder trial of Karen Read, the Massachusetts woman accused of killing her police officer boyfriend in 2022.

The decision came on the fifth day of deliberations and after a nine-week trial in a courthouse outside Boston where Read’s lawyers described the killing of John O’Keefe, 46, as a cover-up carried out by law enforcement officers. 

Prosecutors had argued that Read, 44, and O’Keefe had a tumultuous relationship that culminated with the financial analyst backing her Lexus SUV into her boyfriend and leaving him for dead on Jan. 29, 2022.

Read was charged with second-degree murder, motor vehicle manslaughter while driving under the influence and leaving the scene of a collision causing death.

In a note sent Monday afternoon to Norfolk County Superior Court Judge Beverly Cannone, the foreman said that despite rigorous efforts, the jury of six men and six women remained deadlocked. Some believed the evidence surpassed the standard of proof needed to convict Read, the note said, while others found that prosecutors had not established their case.

In an earlier note to Cannone, the jurors said: “Despite our commitment to the duty entrusted in us, we find ourselves deeply divided by fundamental differences in our opinions and state of mind.”

O’Keefe’s body was found unresponsive that morning, and he was later pronounced dead. The medical examiner attributed his cause of death to blunt force trauma to the head and hypothermia.

Her lawyers alleged that she was framed by officers who sought to conceal a beating that they said O’Keefe suffered during a gathering at the home where his body was found.

The defense alleged that the lead investigator in the case, Massachusetts state Trooper Michael Proctor, manipulated evidence, failed to properly investigate O’Keefe’s death and sent a series of slurs and vulgar messages about Read to friends, family and supervisors.

In his closing argument last Tuesday, Norfolk County Assistant District Attorney Adam Lally acknowledged that Proctor’s texts were “indefensible” but said they had no bearing on the integrity of the agency’s investigation.

Lally dismissed the defense’s claim of a cover-up as “rampant speculation.”

Read repeatedly told first responders that she had hit O’Keefe, Lally said, and vehicle data showed her reversing her SUV for 62 feet at 24 mph near the home of another officer, Brian Albert, after midnight on Jan. 29.

Lally said physical evidence backed up the allegation that she struck him, including a tail light that authorities said was broken after the collision and hair and DNA from O’Keefe that was found on the rear section of the vehicle.

Lally said that no one who attended the gathering recalled seeing O’Keefe inside Albert’s house.

Defense lawyer Alan Jackson said the tail light was actually broken after Read dropped O’Keefe off at Albert’s house, drove home and left in a panic hours later she realized her boyfriend never returned.

The defense presented security video from O’Keefe’s home showing Read backing her SUV into her boyfriend’s vehicle as she left to go find him. Data from O’Keefe’s iPhone showed that his device had gone dozens of steps around the time prosecutors said he was struck, Jackson said, suggesting that those steps could have been to the basement of Albert’s home.

Read’s lawyers were allowed to present a third-party culprit defense — a theory of O’Keefe’s death that differed from the prosecution’s — and they pointed to an agent with the Bureau of Alcohol, Tobacco, Firearms and Explosives who’d traded flirtatious texts with Read as a possible suspect in O’Keefe’s death.

Jackson suggested the agent, Brian Higgins, became angry after Read ignored him at a bar before the gathering at Albert’s home. At Albert’s house, Jackson said, there could have been skirmish between Higgins and O’Keefe over Read that could have ended with O’Keefe falling and hitting his head.

Higgins testified that he never saw O’Keefe inside Albert’s home and he said he was not upset about being ignored by Read.

According to The Associated Press, a forensic engineer who reviewed law enforcement’s handling of the case for the Department of Justice testified that O’Keefe’s injuries should have been more severe had he been struck by a vehicle traveling more than 20 mph.

“We don’t really have enough evidence in this case to determine what one specific event actually caused that injury,” said the expert, Andrew Rentschler, according to the AP.