Sandra Birchmore case: Former police officer Matthew Farwell is accused of killing pregnant woman and faking death as suicide

A former Massachusetts police officer is accused of killing a 23-year-old pregnant woman. He sexually exploited her when she was a teenager and staged her death as a suicide, according to a federal indictment unsealed in Boston on Wednesday.

Former Stoughton police officer Matthew Farwell is accused of strangling Sandra Birchmore in February 2021 after she told him she was pregnant with his child and “staged” her apartment “to make it look like Birchmore had committed suicide,” the indictment states.

He was indicted by a federal grand jury for killing a witness or victim.

“We allege that Sandra Birchmore survived years of sexual harassment, rape, and then sexual violence at the hands of Matthew Farwell, who was employed as a police officer and later as a detective with the Stoughton Police Department throughout their relationship. And when Mr. Farwell realized he could no longer control Ms. Birchmore, he permanently silenced her,” Acting U.S. Attorney Joshua Levy said during a press conference Wednesday.

Farwell, 38, was arrested at a mall Wednesday morning and is scheduled to appear in federal court in Boston Wednesday afternoon, authorities said. ABC News has reached out to Farwell's attorney for comment.

Prosecutors alleged that Farwell befriended Birchmore after she joined a Stoughton Police Department youth program where he was an instructor and “essentially groomed” her.

The indictment alleges the two began a sexual relationship when Farwell was 27 and Birchmore was 15. Farwell allegedly engaged in sexual acts with Birchmore when she was a minor while on duty as a police officer and “falsely claimed he was working certain hours” to cover up the activities, the Justice Department said.

Their affair lasted until her death on February 1, 2021, while Farwell was married and had children, according to prosecutors. She was found dead in her Canton apartment on February 4, 2021.

Prosecutors allege that after Birchmore told Farwell in October 2020 that she wanted a child of her own, the two “entered into an agreement”: He would try to impregnate her “in exchange for her silence about his criminal conduct (i.e., child sexual abuse) and their years-long extramarital affair,” according to a motion supporting the pretrial detention.

Prosecutors allege that after Birchmore told Farwell in December 2020 that she was pregnant and wanted him to be more involved in planning the birth, she became angry and “lost control.”

“The information she had about his illegal behavior threatened to leak out,” Levy said. “In fact, word of their relationship got around.”

Less than two weeks before Birchmore was found dead, a friend called Stoughton police and reported Birchmore and Farwell's sexual relationship, according to the Justice Department. Farwell reportedly became “visibly angry” when he learned of the call and “began to lose his patience.” She also told friends that he had become physically violent toward her, Levy said.

In one case, Farwell allegedly had pregnant Birchmore in a headlock and told her he wished she were dead, prosecutors said.

“Then on February 1, 2021, everything came to a head,” Levy said.

Prosecutors allege Farwell went to Birchmore's apartment that night wearing a mask “despite being known to oppose COVID-19 mask mandates” and strangled her with the strap of a duffel bag, court records say. He then “used his knowledge and experience as a police officer” to stage her death to make it look like a suicide, Levy said.

He allegedly repeatedly lied about the nature of their relationship to Massachusetts State Police investigators investigating her death, according to Steve Kelleher, the FBI special agent in charge in Boston. He allegedly told investigators that their sexual relationship began in 2020 — even though text messages with Birchmore showed it began in 2013, prosecutors alleged in court documents. He also allegedly told investigators that they last had sex in October 2020 “to avoid suspicion that he is the father of Birchmore’s unborn child,” even though “text messages indicate that Farwell met with Birchmore to have sex after that date,” court documents say.

According to court documents, before her death, Farwell allegedly instructed Birchmore to delete evidence of their sexual relationship.

“He tried to cover his tracks, to literally get away with murder, and he almost succeeded, to this day,” Levy said.

State officials initially believed Birchmore's death was suicide. But Levy said federal investigators uncovered “significant new information” and reviewed existing information over the past year, leading to the charges. Levy did not elaborate on what initially prompted federal authorities to investigate Birchmore's death.

Kelleher said investigators reviewed tens of thousands of text messages, emails and financial records, conducted dozens of interviews and analyzed the crime scene as part of their investigation.

He said the investigation had “uncovered evidence that was inconsistent with suicide” – including the fact that in the hours before her death, Birchmore had contacted a photographer to ask about a photo shoot for her newborn and a friend to get baby clothes.

He also said she was doing laundry when she died, calling the alleged murder “depraved.”

“Committing murder to eliminate victims and witnesses is abhorrent and shakes the very core of our justice system, which relies on people to truthfully testify about what they know,” he said.

If convicted, Farwell faces a minimum sentence of life in prison. This charge also carries the death penalty. Levy said the Justice Department has not yet made a decision on whether to seek the death penalty.

Levy said they are sharing their information with local and state authorities so they can assess whether any state charges might be warranted.

According to the indictment, Farwell worked as a police officer and then as a detective for the Stoughton Police Department from March 27, 2012, to April 1, 2022.

Stoughton Police Chief Donna McNamara said the police department assisted the FBI in its investigation that led to the charges.

“The alleged murder of Sandra is a horrific injustice,” McNamara said in a statement. “The allegations against the suspect, a former Stoughton police officer, represent the worst case of not only professional misconduct but human indecency that I have witnessed in my nearly three-decade career in law enforcement.”

If you or someone you know is going through a mental health crisis, call or text 988 Suicide. & Crisis Lifeline at 988.