Matthew Farwell's twin brother William continues testimony in Sandra Birchmore trial

Matthew Farwell's twin brother William is back on the stand Tuesday at federal court in South Boston.

Matthew Farwell, a former Stoughton, Massachusetts police officer, is accused of killing 23-year-old Sandra Birchmore and her unborn baby at her apartment in Canton in February 2021. Prosecutors say he staged it to make it look like a suicide to cover up a years-long affair with Birchmore that began when she was just 15.

Farwell is now on trial for killing a witness or victim and causing the death of an unborn child. He has pleaded not guilty to both charges.

His twin brother, William, took the stand late Monday afternoon for about half an hour. He admitted having his own sexual relationship with Birchmore, but he's testifying under the promise of federal immunity because he could be charged with a criminal offense for having sex while on duty as a police officer.

William "Billy" Farwell told the jury his affair with Birchmore began when she was 20 and at the time he did not know she was having sex with his brother. Billy Farwell had his police certification permanently revoked in 2024.  

Text messages displayed during testimony on Tuesday shows that Birchmore texted William Farwell in May of 2019 to say that his brother found out about their sexual relationship.

"We got into a massive fight and I was told I have to re-earn trust and everything," Birchmore texted.

William Farwell testified that he never had a conversation about their respective relationships with Birchmore. 

Matthew Farwell's attorney did not deny her client and Birchmore had an affair, but she said Farwell never thought the baby was his and when he broke up with Birchmore, she killed herself. DNA testing later confirmed the father of Birchmore's unborn child was Jason Pickard, a U.S. Army recruiter who was also having a sexual relationship with Birchmore. He also testified in the trial under an immunity agreement.

If convicted, Matthew Farwell faces a mandatory sentence of life in prison.