A cellphone data analyst and a close friend of the victim testified this week in the high-profile retrial of Karen Read, the Massachusetts woman charged with killing her boyfriend, a Boston police officer, in January 2022.

The judge in the case declared a mistrial last July when jurors could not agree on a verdict. The retrial is unfolding in the same courthouse in Dedham, south of Boston.

Prosecutors say that Ms. Read, 45, intentionally backed her car into Officer John O’Keefe and killed him after a night out drinking with friends. Defense lawyers argued in the first trial that after Ms. Read dropped Officer O’Keefe off at a party late that night in suburban Canton, Mass., at the home of another Boston police officer, he was beaten and left for dead in the front yard during a raging blizzard.

Ms. Read has pleaded not guilty to charges of second-degree murder, manslaughter while operating under the influence of alcohol, and leaving the scene of an accident causing death.

The defense contends that she is the victim of a corrupt and incompetent investigation by law enforcement officials who conspired to frame her for the murder.

Cellphone data is disputed

A digital forensics expert, Ian Whiffin, testified this week about his analysis of data from the Officer O’Keefe’s cellphone, which was found beneath his body. Based on the data, Mr. Whiffin said, he believes that the phone was in the yard of the home where the party was held from 12:30 a.m. on Jan. 29, when Ms. Read dropped off Officer O’Keefe there, until 6 a.m. that morning, when his body was discovered in the snow.