BOSTON — Federal prosecutors are asking a judge to keep former Stoughton Police Department detective Matthew Farwell detained while awaiting trial in the death of Sandra Birchmore, citing newly reviewed cellphone evidence they say shows he poses a danger to the community and a risk of obstruction and flight.
Farwell is accused of killing Birchmore by strangling her on February 1, 2021, and then staging her Canton apartment to make it look like a suicide after she informed him he was the father of her unborn child. He was also a married father of three at the time. Prosecutors allege the killing was carried out to conceal an ongoing sexual relationship between Farwell and Birchmore that they say began when she was under 18.
In a second supplemental memorandum in support of a motion for detention filed this week in U.S. District Court in Massachusetts, prosecutors said data from an iPhone seized from Farwell reveals concerning online activity and communications uncovered after the defense recently turned over a filtered version of the phone’s contents.
The FBI seized Farwell’s iPhone in August 2024 pursuant to a search warrant, according to the filing. Prosecutors said Farwell’s attorneys reviewed the data first and withheld more than 80,000 communications before providing the government with the remaining material earlier this month.
A preliminary review of the disclosed data revealed information not available when earlier detention filings were submitted and supports keeping Farwell in custody pending trial, prosecutors said.
Prosecutors said the phone data shows that in 2021 and 2022 — after the death of Birchmore — Farwell accessed pornographic material, which they say suggests a continued sexual interest in teenage girls. One video cited in the filing was accessed in November 2022 and included language describing a “barely legal teen.” Additional video titles referenced “teen” and “step-sister” themes, according to the memorandum.
The government argues that Farwell’s post-offense activity is relevant to assessing his potential danger, citing earlier allegations that he began a sexual relationship with Birchmore in 2013, when she was 15 years old and enrolled in the Stoughton Police Explorers Program, and he was a police officer instructor in his late 20s.
Prosecutors also pointed to evidence they say demonstrates a risk of obstruction. According to the filing, Farwell used the privacy-focused search engine DuckDuckGo — rather than his phone’s default browser — to search for information about Birchmore and matters related to her death and the investigation. The government said those actions suggest efforts to conceal online activity.
The filing further describes evidence the government says indicates a risk of flight or nonappearance. Prosecutors said that on June 24, 2024 — the day it was widely reported that a forensic pathologist concluded Birchmore died by homicidal strangulation — Farwell wrote a note to a close friend using his phone’s Notes application.
In the note, Farwell wrote that he wished “this had all gone a different way,” asked the friend to help care for his wife and children, and said he would see the friend “on the other side,” according to the court filing. Prosecutors wrote that while the note contains what they describe as a self-serving false statement, it reflects a shift in Farwell’s state of mind once Birchmore’s death was publicly labeled a homicide by an expert.
Farwell did not flee at that time, the government acknowledged, but prosecutors argued that the message demonstrates ideation courts have previously considered relevant in evaluating flight risk.
The government is asking the court to order Farwell detained pending trial. Prosecutors also requested that, if the judge is inclined to release him under conditions, the order be stayed to allow the government to seek review.
Farwell is facing federal charges in connection with Birchmore’s death. His attorneys have opposed detention in earlier filings. No hearing date was immediately listed in the memorandum.
Farwell recently asked to be released on $50,000 bail, while Birchmore’s family is asking a court to issue a no‑contact order against his defense team.
He also asked the judge presiding over the case to throw out some evidence last week.
Authorities have said that Farwell’s DNA was found on a strap that prosecutors allege was used to kill Birchmore, as well as her underwear.
Farwell has pleaded not guilty to the charges against him.
His trial is scheduled to begin in October.
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