The John J. Moakley courthouse stands on the Boston waterfront, and on Friday, October 9, 2026, it was full. Local and national reporters came, members of the public came, and so did the true-crime influencers who now trail every famous trial with their phones held up. The Boston Globe reported that the building buzzed. Only weeks earlier the Lindsay Clancy trial ended without a verdict, and much of the same crowd had moved on to this one.

The trial is over the death of a young woman in Canton, Massachusetts, in February 2021. The jury that took four days to choose, after selection began on October 5, heard two versions of what happened to her. Each side had 45 minutes.

“There’s been a lot of anticipation. It’s been a long wait,” Barbara Wright, Sandra Birchmore’s cousin, said outside the courthouse.

The program

It began at the police station. In 2010, the year she turned 13, Birchmore joined the Stoughton Police Department Explorers Program, a scheme meant to bring young people closer to the police. Matthew Farwell had been an Explorer himself as a boy and stayed on as a volunteer instructor. According to the US Attorney’s Office announcement of his arrest, he was a sworn Stoughton officer from about March 27, 2012, until about April 1, 2022.

Prosecutors say the two began having sex when she was 15. NBC Boston’s recap put him at 27 then. Massachusetts sets the age of consent at 16, and Assistant US Attorney Torey Cummings kept calling it what the law calls it: rape. Prosecutors say the relationship went on, broken off and resumed, until the day she died. More than 40,000 text messages passed between them. Both sides will build their case on those messages.

Farwell is now 40. He has pleaded not guilty. If convicted, he faces life in federal prison.

The prosecution’s account

Cummings told the story in order, as a slow tightening. Birchmore, she said, was infatuated with Farwell, called him her best friend and wanted a child with him. Then, in late 2020, she learned that he was married and that his wife was expecting their third child. According to the texts, she threatened to reveal the relationship, including that it started when she was a minor, unless he got her pregnant. Cummings said he agreed. They tried for a few months, and she was pregnant just before New Year’s.

Cummings said Birchmore’s messages to friends in those weeks were full of joy. She booked a maternity photo shoot and was looking after her body and her mind. Farwell, the prosecutor said, panicked. On January 20, 2021, one of Birchmore’s friends told a police dispatcher that the two were having sex. After he found out, Cummings said, he “put his hands on” her. His wife was due at the start of February.

“It was no longer whether his crimes would be exposed — it was when. She could end his life with the information she had. So he was going to end hers first.”

“He had lost control of Sandra,” Cummings said. “He needed a way to silence her.” Prosecutors say he went to her apartment wearing a medical mask and strangled her. The two had often texted about rough sex, choking among it, so she would not have been alarmed when his hands went to her throat until it was too late. The government says this happened on February 1, 2021, and that he then staged the scene to look like suicide. Prosecutors told the jury it happened 24 hours before his wife gave birth, according to People’s account via AOL.

Testing later showed that Farwell was not the father. The prosecution says this matters little, because at the time both of them believed he was.

The defense’s account

Kimberly Stevens, for the defense, did not deny much of this. Yes, there was an affair. Yes, Farwell went to Canton that night. He did not go there to kill her, she said.

“Matt Farwell broke up with Sandra Birchmore and said, ‘It’s not my baby,’” Stevens said. “In an impulsive act of despair, she took her own life.”

Stevens described weeks of decline. She told jurors Birchmore was almost out of money, had little family support and was anxious about the pregnancy, searching online about spotting and bleeding. Her texts and searches, the lawyer said, suggested she felt the “walls were closing in.” On her last day she wrote that she had fallen, that she could not sleep, that she needed him. Photos on her phone mentioned suicide. “That’s a window into her mental state as this is all happening,” Stevens said. NBC Boston reported that she also cited a search: “What color is the suicide ribbon?”

Stevens said Birchmore had tried to take her own life before, and that an ex-boyfriend once wrote in an affidavit that she told him she would kill herself and blame him. She said Farwell’s DNA was not found under Birchmore’s fingernails, which she took as a sign there had been no struggle. According to Stevens, he wore the mask and hood so his wife would not find out, and he had already worked out from the timing that the child could not be his.

The state that looked away

State investigators first called the death a suicide. Federal investigators concluded she was killed, and the state medical examiner then changed the cause of death to undetermined. Murder is normally a state prosecution, but Norfolk District Attorney Michael W. Morrissey would not bring one. Washington stepped in.

Cummings went after the district attorney’s office for the suicide finding. She said the State Police unit that investigates Norfolk County homicides did little work and still pushed for that conclusion. It is the same unit that drew criticism in the Karen Read case, and some of the same officers are expected to testify.

The federal charge is narrower than murder: killing a witness or victim. Prosecutors must prove that Farwell killed Birchmore, that he meant to, and that he did it to keep authorities from learning of three other alleged crimes. These are deprivation of rights under color of law, the statute usually used for police abuse of power; coercion and enticement; and wire fraud, on the theory that he lied about his hours so they could have sex while he was on duty. A superseding indictment added a count over the death of her unborn son.

So the case turns on the motive of a man who wore a badge and on the crimes that badge allegedly let him commit. The trial is expected to last about five weeks, with testimony on grooming, child sexual abuse and suicide, and technical expert evidence on how Birchmore died. Testimony begins Tuesday.