A former Massachusetts police officer is on federal trial for murdering a 23-year-old pregnant woman who was making plans for her baby — and the initial investigators called it suicide, because nobody bothered to ask what the cop had done to her.

Sandra Birchmore was found dead in her Canton apartment on Feb. 1, 2021, hanging from a closet doorknob. Massachusetts State Police and the state medical examiner ruled it a suicide. They didn't know about the decade of alleged sexual abuse by Stoughton police officer Matthew Farwell. Once federal prosecutors took over and that history came to light, the medical examiner changed the ruling to undetermined. Now a jury will decide whether Farwell groomed Birchmore from childhood, strangled her with a duffel bag strap, and staged the scene — or whether, as the defense claims, a jilted Birchmore took her own life after Farwell told her he wasn't the father.

Birchmore's family isn't buying the suicide story. "She was thrilled to be pregnant," her cousin Barbara Wright said outside Boston's federal courthouse Friday. "She loved having her new apartment, and she was making plans. So it's not what I saw."

Prosecutor Torey Cummings laid out a damning timeline. Birchmore joined the Stoughton Police Explorer program at age 12 — her mother thought it would give her positive role models. Instead, Farwell, a volunteer instructor, sent her a Facebook friend request and began grooming her under the pretext of "tutoring." He allegedly raped her for the first time on April 10, 2013, when she was 15 and he was 27. "That's a crime," Cummings told the jury — a line she repeated. Text messages shown in court had Farwell telling the girl the day he first had sex with her "was the best day of my life" and that he couldn't wait to "f—k" her again. He also shared sexual fantasies involving "domination, causing pain and rape," Cummings said.

The relationship continued for eight years, even while Farwell was on duty. When Birchmore learned Farwell's wife was pregnant with their third child, she threatened to expose him if he didn't impregnate her, the prosecutor said. Birchmore learned she was pregnant on Dec. 8, 2020. Farwell's response, according to Cummings: "You are truly the worst person on the face of Earth."

But then Farwell made what Cummings called "a complete 180." He stopped acting angry. He asked for a key to her apartment. He scoped out her closet and bathroom — something Birchmore texted a friend was "weird" on Jan. 24, 2021. Nine days later, Farwell texted at 9:07 p.m.: "Are you still up. Ok to come by for a second." Birchmore responded: "Yeah you can come say hi. You ok? Doors open when you get here." Surveillance footage showed the 6-foot-4 cop entering her building at 9:14 p.m. wearing a blue mask — despite being outspokenly anti-mask during COVID. He left about an hour later. Prosecutors say he strangled the 5-foot Birchmore, seated her body by the closet door, and latched a duffel bag strap around her neck and the doorknob. Eight days later, her body was found.

DNA testing later revealed Farwell was not the father of Birchmore's unborn child — though both believed he was at the time. The New York Post reported that Farwell allegedly killed her the day before his wife gave birth to their third child.

The Boston Herald noted that Cummings slammed the Massachusetts State Police assigned to the Norfolk DA's office for failing to investigate the case. The medical examiner initially ruled suicide without knowing the abuse history. That's the same system that was supposed to protect a 12-year-old girl who walked into a police program looking for mentors.

A young woman who couldn't wait to be a mother is dead, and the people who were supposed to protect her either failed or looked the other way. The trial will answer whether Farwell killed her. The harder question is why it took the feds to even ask.