Judge Denise Casper addressed the panel after receiving notes from jurors, telling them to take the time they need and noting that the court cannot stay open past 6 p.m. but that they are free to return day after day to complete their duty. She then sent them back to continue deliberating.

If the impasse persists, Casper could issue what is known in Massachusetts as a Tuey-Rodriguez charge — the state-court term for the supplemental instruction known in federal court as the Allen charge. The instruction urges jurors to set aside their differences and work toward a unanimous verdict. Legal analysts following the case said such a charge is likely if the jury remains stuck.

Farwell, now 40, is accused of killing Birchmore, 23, on Feb. 1, 2021, and staging her death as a suicide after learning she was pregnant with what he believed was his child. Prosecutors say he acted to prevent her from reporting that he had begun sexually abusing her when she was 15 and participating in a Stoughton police youth program.

In closing arguments, Assistant U.S. Attorney Brian Fogarty told the jury that Farwell did not go to Birchmore's apartment that night for a clean break. "He went to clean up the mess he created for himself years earlier, a mess that could bring serious charges and destroy his life," Fogarty said. "He cleaned up the mess by taking Sandra's life."

Defense lawyer Kimberly Stevens acknowledged an extramarital relationship but said Farwell did not kill Birchmore and did not have sex with her until she was old enough to consent under Massachusetts law. The defense argued that Birchmore had threatened suicide before and was devastated when Farwell came to her apartment to end the relationship. "When all is lost and all hope is gone and you're alone in the world, are you going to pick your phone up?" Stevens asked the jury. "Or did she sit down and take that strap and make the pain stop?"

The nearly monthlong trial featured about 50 witnesses and 500 exhibits. It unfolded in federal court in part because local prosecutors never brought criminal charges.

Massachusetts State Police investigators, some with personal ties to Farwell, quickly concluded Birchmore's death was a suicide after she was found on her apartment floor with a strap around her neck. The state medical examiner's office, relying partly on police information, initially ruled the death a suicide but has since changed the manner of death to "undetermined."

Birchmore's friends and family never accepted that conclusion. She had told dozens of friends about her pregnancy and, according to prosecutors, was excited to become a single mother. A stroller still in its box was found in her apartment, along with an ultrasound photo on her refrigerator.

The FBI began investigating in 2023, partly at the urging of a former Stoughton deputy chief who had led an internal affairs inquiry into Farwell. Federal investigators concluded the local probe was rushed and compromised: Farwell was interviewed for only about 15 minutes in a parking lot, investigators took no notes, did not examine him for injuries or collect his DNA, and looked at his phone only after he had deleted texts with Birchmore.

The FBI recovered roughly 40,000 texts between Farwell and Birchmore, including messages in which they reminisced about having sex when he was 27 and she was 15 — too young to consent under state law. The messages also showed the relationship growing contentious as Birchmore pressed Farwell to get her pregnant and threatened to tell his wife.

Prosecutors argued Farwell feared Birchmore would contact law enforcement about his crimes and became more controlling, tracking her phone and ordering her to delete compromising communications. Texts from late 2020, after she was pregnant, showed the two arguing over what role, if any, Farwell would play in the child's life. A paternity test after Birchmore's death revealed another man was the father.

Twelve days before she died, a friend of Birchmore called the Stoughton Police Department to report the affair.

A digital forensics expert testified that on the night of Birchmore's death her phone stopped moving three minutes before the lobby security camera recorded Farwell leaving her building. Dr. William Smock, an expert hired by prosecutors, testified that Birchmore's injuries indicated she was strangled with a duffel bag strap and struggled before dying, noting that her glasses were not near her body and a pair of flip-flops were overturned. A defense expert, Dr. Thomas Andrew, the former chief medical examiner in New Hampshire, disputed Smock's conclusion that the death was a homicide.

Jurors deliberated for a little more than three hours Friday before going home for the weekend. They return Tuesday morning to resume their work.