Suicide, or murder? Trial begins for Massachusetts ex-cop accused of killing his pregnant lover

By Faith Karimi

Boston (CNN) — The trial of a former police officer accused of killing his young lover five years ago in her suburban Boston apartment opened Friday with two vastly different accounts of Sandra Birchmore’s final days.

Birchmore, 23, was found slumped on her bedroom floor in Canton, Massachusetts, with a duffel bag strap looped around her neck and tied to a closet door handle. Local and state authorities ruled her February 1, 2021, death a suicide, but federal prosecutors took up the case three years later and charged former Stoughton police officer Matthew Farwell with killing her. He has pleaded not guilty.

Assistant U.S. Attorney Torey B. Cummings told jurors that Farwell was supposed to be a mentor to Birchmore but first had sex with her when she was 15 and he was 27. Cummings said he exploited her for years – sometimes meeting Birchmore for sex while he was on duty – and ultimately killed her after she became pregnant and he feared exposure of their secret relationship.

“She could end his life with the information she had, so he decided to end hers first,” Cummings said.

But defense attorney Kimberly Stevens portrayed Birchmore as an anxious, lonely and struggling young woman who had less than $3 in her bank account and became suicidal after Farwell broke up with her. Stevens conceded that the married Farwell had an affair with Birchmore and had made mistakes, but insisted to jurors that he didn’t kill her.

Instead, Stevens told jurors, Birchmore killed herself in an “impulsive act of despair” after Farwell broke up with her that night.

Birchmore’s family pressured investigators to reconsider the suicide ruling, saying she was planning her future and excited to be a mother. A federal investigation led to Farwell’s indictment in 2024, and in April the medical examiner’s office changed the manner of Birchmore’s death to “undetermined.”

Farwell, 40, is charged with killing a witness or victim – essentially, to stop Birchmore from potentially incriminating him. (It’s a federal offense to engage in a sexual act with someone under the age of 16 if the other person is at least four years older.) He also faces a second charge – related to Birchmore’s pregnancy – of violating a federal law protecting unborn children.

DNA testing later ruled Farwell out as the father of Birchmore’s unborn baby. But prosecutors have said he believed the child was his at the time of her death.

Farwell has been decertified as a police officer and barred from working in law enforcement in Massachusetts. He has been in jail since his August 2024 arrest, and if convicted faces a potential sentence of life in prison.

His trial, at the John J. Moakley Courthouse in Boston, is expected to last about a month.

‘He gave her the attention she craved’

Cummings portrayed Birchmore as a vulnerable young woman who grew up idolizing police officers, only to be groomed by one who used and discarded her.

A stoic-looking Farwell sat between his two female attorneys in a charcoal gray suit and mostly stared at a computer screen on the defense table as Cummings presented the prosecution’s case. Occasionally, he glanced to his right at the jury box, where 16 jurors– including four alternates and six women – sat watching.

Cummings referred to Farwell as “the defendant” throughout, in sharp contrast to Stevens, who called him “Matt” during her opening statement and at one point put her arm on his shoulder.

Six of Birchmore’s cousins were in the courtroom Friday for opening statements, a family member told CNN.

Birchmore’s mother had faced a series of health problems and Birchmore’s father was not in the picture, Cummings said. So in 2010 Birchmore’s mother enrolled her daughter in the Stoughton Police Department’s Explorers program for local youths, hoping she’d get structure and meet positive role models.

The teen had struggled in school, was diagnosed with ADHD and found it difficult to make friends, Cummings told jurors. The prosecutor displayed a group photo of kids in the Explorers program, and pointed out that at 5 feet, Birchmore was the littlest.

Birchmore was “enamored” with police officers and spent many hours at the police department, Cummings said. Farwell was one of the officers she trusted, and in late 2012, when Birchmore was 15, he sent her a Facebook friend request and later started tutoring her at a local library, according to the prosecutor. But what started as a mentoring relationship quickly turned sexual, Cummings said.

“He gave her the attention she craved,” she said. Cummings described an illicit sexual relationship that continued for some eight years. It was built on secrecy and control and included rape fantasies and rough sex initiated by Farwell, the prosecutor said.

Authorities discovered some 40,000 messages between Farwell and Birchmore on her electronic devices that offered a digital trail of a relationship that started when she was a minor.

“He told her the day he took her virginity when she was 15 was the best day of his life,” Cummings told the jury, referring to one text-message exchange. “Sandra’s first sexual experience involved a crime,” she added.

Farwell got married in May 2013, about a month after he and Birchmore first had sex, Cummings said. After Birchmore learned that Farwell was expecting his third child with his wife in February 2021, she began pressuring him to have a baby with her and threatened to tell his wife, the prosecutor added.

“She was going to expose his crime … for the last 10 years,” Cummings said.

The prosecutor said Farwell agreed to her demands to appease her and keep their relationship a secret. But “she kept asking for more, she kept changing the terms of the deal,” Cummings told jurors. “The defendant was not happy about it.”

Cummings said that in January 2021, a friend of Birchmore’s called Stoughton police and told a dispatcher about the illicit relationship, infuriating Farwell.

She also said Birchmore had told a few people she planned to share the news about her baby publicly on Valentine’s Day and had prepared a poster for social media saying, “I’m expecting a new little one to love.”

Cummings told jurors that on the evening February 1, 2021, Farwell texted Birchmore and asked whether he could come over. She told him she’d leave the door unlocked. It was the final outgoing message on her phone.

Farwell arrived four minutes later wearing a dark hoodie and a medical mask, the affidavit said. Surveillance video, which Cummings played for jurors, showed him entering her building and then leaving about half an hour later.

Cummings told jurors that Farwell staged his crime to look like a suicide and believed that people would accept that finding because Birchmore was a vulnerable young woman.

But authorities found his DNA on the duffel strap around Birchmore’s neck, she said.

‘The government has not met its burden’

Stevens, the defense attorney, offered a different explanation for Farwell’s visit that night. In her opening statement, she said he went to Birchmore’s apartment to break up with her.

She portrayed Birchmore as an unstable woman who texted Farwell relentlessly, including on the day she died. Stevens read some of the texts aloud to jurors:

“I’m sorry, I’m needy today. Can I text you tomorrow before the snow comes?”

“I took my medicine just to let you know.”

“I wish you were here with me tonight, sad face.”

“I keep waking up.”

“I couldn’t sleep last night.”

Stevens said the barrage of text messages showed a young woman who was struggling with anxiety.

“She fantasized about having a relationship that would produce a child and a home she never had,” she told jurors.

“That’s a window into her mental state. Thanksgiving alone, Christmas alone, no family,” she added. Birchmore couldn’t afford her rent and had expressed fears that she was spotting and that her pregnancy was at risk, Stevens said.

When her body was found Birchmore was wearing turquoise leggings and a dark puffy jacket, and neither showed tears or other signs of a struggle, Stevens said. She also said that Farwell’s DNA was not found under Birchmore’s fingernails, and that the ligature found around her neck contained DNA from several people – not just Farwell.

“Mixture evidence is never evidence,” Stevens told jurors. “At the close of evidence, you’ll find that the government has not met its burden beyond a reasonable doubt.”

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