Ex-Cop Accused of Grooming Teen Cadet and Killing Her and Their Unborn Child as Defense Claims She Died by Suicide

Jury selection started on Tuesday, October 6, in the federal case against former Stoughton, Mass., police detective Matthew Farwell, who prosecutors claim killed Sandra Birchmore in 2021 and then staged it as a suicide.

Prosecutors say Farwell, 40, groomed and sexually exploited Birchmore for years after meeting her through a police youth program when she was a minor, while defense attorneys argue that the 23-year-old, who was pregnant at the time of her death, took her own life.

Farwell met Birchmore through the Stoughton Police Explorers program, where he volunteered. Prosecutors allege he began a sexual relationship with Birchmore when she was 15 years old and he was 27. In January 2021, a friend of Birchmore’s contacted the Stoughton Police Department reporting that there was a sexual relationship between Birchmore and Farwell. Prosecutors say a department employee told Farwell about the call.

Several days later, in February 2021, Birchmore’s body was discovered in her Canton apartment. Federal prosecutors allege that Farwell strangled Birchmore after she had informed him that she believed he was the father of her unborn child, and that he killed her the day before his wife was scheduled to give birth to their third child. Prosecutors also allege that Farwell killed Birchmore to prevent her from revealing to authorities that he had coerced her into a sexual relationship while she was a minor.

Farwell’s attorneys say that after the two had an argument at Birchmore’s apartment, he told her he wasn’t the father of her baby and that their relationship was over. DNA testing later excluded Farwell as the biological father of Birchmore’s unborn son. At the time of Birchmore’s death, she was approximately eight to 10 weeks pregnant.

Birchmore’s death was originally ruled a suicide, and the defense believes that ruling is still accurate. The medical examiner later amended the manner of death to undetermined, and Farwell was arrested in August 2024. He has pleaded not guilty.

The charge against Farwell for killing a witness or victim carries a mandatory life sentence. A second count was added in a superseding indictment in October 2025 that relates to the death of Birchmore’s unborn child. In December 2025, the Justice Department stated it would not pursue the death penalty.

While awaiting trial, Farwell has been held without bail at a Rhode Island detention facility. U.S. District Judge Denise Casper denied Farwell’s most recent motion to move the trial out of Massachusetts after previously denying his January request to move it to Rhode Island, according to a report.

Casper is presiding over the trial at the Moakley federal courthouse in Boston. “The jury is central to the administration of justice,” Casper said to potential jurors. “Both parties have a right to a jury that is fair and impartial.”

By Friday, October 9, a jury of 16 members, including four alternates, could be seated. Opening statements could begin that day. Casper instructed potential jurors to avoid news reports and any conversations about the trial.

More than 100 witnesses could testify at the trial, and jurors are expected to see thousands of text messages between Farwell and Birchmore. No cameras are permitted in federal courtrooms, so the public won’t be able to see the trial via a live feed. The trial is expected to last about a month.