Matthew Farwell trial heads to closing arguments in pregnant woman's killing

Prosecutors say Farwell tried to stage her death as a suicide

Closing arguments are expected Friday in the federal trial of Matthew Farwell, a former Massachusetts police officer accused of killing Sandra Birchmore, a pregnant 23-year-old, in 2021. Farwell, now 40, was a married detective with the Stoughton Police Department at the time of her death. Birchmore had participated in a youth program at the department as a child.

Federal prosecutors say Farwell killed Birchmore and tried to stage her death as a suicide after learning she was pregnant with what he thought was his child, to keep her from revealing a sexual relationship they say began when she was 15 — too young to consent under Massachusetts law.

His lawyers acknowledge the extramarital relationship. But they say he did not kill Birchmore and did not have sex with her until she was an adult.

The trial has unfolded in federal court in Boston, partly because local prosecutors never brought criminal charges in the death. Federal investigators later concluded the original local probe was rushed and compromised: Farwell was interviewed for just 15 minutes in a parking lot, investigators took no notes, did not examine him for injuries and did not sample his DNA, and police reviewed his phone only after he had deleted his texts with Birchmore.

Local police and Massachusetts State Police investigators — some with personal connections to Farwell — quickly concluded that Birchmore’s death was a suicide after she was found slumped on her apartment floor with a strap around her neck. The state medical examiner’s office, relying partly on information from police, initially ruled that Birchmore died by suicide; the office has since changed the official cause of death to “undetermined.” Birchmore’s friends and family never believed the teacher’s aide had killed herself.

The FBI began looking into the death in 2023, partly at the urging of a former deputy chief at the Stoughton department who had led an internal affairs investigation into Farwell and several other officers accused of misconduct. Farwell’s twin brother, Billy Farwell, testified that the lead local investigator — a longtime family friend — told him he wanted the case closed and needed the investigation like he needed a “bullet in the head.”

The FBI’s work uncovered about 40,000 texts between Farwell and Birchmore, including some in which, prosecutors said, the two reminisced about having sex when she was 15. The messages also showed the relationship growing contentious as Birchmore pressed Farwell to get her pregnant and threatened to tell his wife if he did not. After Birchmore learned of her pregnancy in late 2020, the texts recorded arguments over what role, if any, Farwell would play in the child’s life.

A digital forensics expert testified that Birchmore’s phone stopped moving at 9:40 p.m. on Feb. 1, 2021 — three minutes before a lobby security camera recorded Farwell leaving her building on the night of her death.

The two sides offered competing medical accounts. Dr. William Smock, an expert hired by prosecutors, testified that Birchmore’s injuries indicated she was strangled with a duffel bag strap and that she struggled before dying. Dr. Thomas Andrew, the former chief medical examiner in New Hampshire, testified for the defense that the evidence pointed to hanging and dismissed Smock’s determination that the death was a homicide.

Prosecutors pointed to Birchmore’s final weeks as those of a woman preparing for a child: she had told dozens of friends about her pregnancy and, according to prosecutors, was thrilled to start her next chapter as a single mom. She had booked a maternity shoot, was searching for a venue for her baby shower and was considering baby names. A stroller still in the box was found in her apartment, along with an ultrasound photo pinned to her refrigerator.

Farwell’s lawyers say he went to Birchmore’s apartment to break up with her, not to kill her, and that Birchmore — broke and alone when she became pregnant, in their account — took her own life. A paternity test later revealed that a different man was the father of her unborn child. His legal team also leaned on Birchmore’s mental health history, saying she began taking psychiatric medication at age 6, attempted suicide as a teenager and wrote about suicide several times in her journals.