Twin brother returns to stand in South Boston murder trial

William Farwell returned to the witness stand Tuesday at federal court in South Boston to continue his testimony in the trial of his twin brother, Matthew Farwell. The former Stoughton police officer is accused of killing Sandra Birchmore, 23, and her unborn child in their Canton apartment in February 2021. Prosecutors argue Matthew staged the scene to appear as a suicide while hiding a relationship that began when Birchmore was 15.

Matthew Farwell has pleaded not guilty to charges of killing a witness and causing the death of an unborn child. If found guilty, he faces a mandatory life sentence. His defense attorney conceded that Matthew and Birchmore had an affair but argued that Matthew believed the child was not his. She maintained that Birchmore ended her own life after the breakup.

William Farwell, known as Billy, took the stand for approximately 30 minutes late Monday afternoon. He spoke under a federal immunity agreement that protects him from prosecution for having sexual relations while on duty. Billy told the jury that his relationship with Birchmore started when she was 20. He stated that he did not know at the time that his brother was also involved with her.

The defense presented evidence that DNA testing identified the father of Birchmore's unborn child as a different man. This individual, a U.S. Army recruiter who also maintained a sexual relationship with Birchmore, testified earlier in the trial under a similar immunity deal. The case hinges on conflicting accounts regarding the nature of the relationships and the cause of death.

Billy Farwell is scheduled to resume his testimony Tuesday. The jury will hear further details about the timeline of events leading up to the February 2021 incident in Canton. Both brothers' relationships with Birchmore are central to the prosecution's theory of the case.