Prosecutors Seek Affair Testimony in Farwell Murder Trial

Federal prosecutors asked a judge to allow three women who allegedly had affairs with former Stoughton police detective Matthew Farwell to testify in his murder trial, arguing their testimony could challenge the defense explanation for his actions during the 2021 death investigation.

The motion was filed over the weekend after prosecutors said defense attorney Kimberly Stevens's opening statement made the alleged affairs relevant. Farwell is accused of killing Sandra Birchmore and staging her death as a suicide at her Canton apartment in 2021.

According to prosecutors, they previously sought limited testimony about at least three extramarital affairs involving Farwell, but the judge denied that request. They argued the issue should be reconsidered after the defense described Farwell's conduct as related to hiding infidelity.

The defense argument included Farwell's decision to wear a COVID mask while visiting Birchmore's apartment on the day of her death, which prosecutors said was different from his behavior in other relationships.

Prosecutors described the proposed evidence as "specially relevant" in their motion seeking to admit testimony about Farwell's alleged affairs.

Defense attorney Kimberly Stevens was identified by prosecutors as saying Farwell's conduct, including the mask, "was merely evidence of an innocent man's desire to hide his infidelity from his wife."

The prosecution motion stated that the three women would provide testimony about Farwell's behavior in those relationships.

"Farwell’s adult affair partners will offer critical testimony that strikes at the heart of Farwell’s disclosed defense and Attorney Stevens’s purported innocent explanations for Farwell’s mask-wearing. The three affair partner witnesses will say Farwell never took steps to hide their encounters. He never wore a mask or disguise.

In fact, he had a cavalier attitude about their encounters. With this evidence, the jury will know that Farwell, an ardent anti-masker, was doing something on Feb. 1, that he did not do with his other adult affair partners. Farwell's attempt not to be seen when he went to Ms.

Birchmore's apartment proves that he was there to kill Ms. Birchmore, and not merely present as a cheating spouse afraid that his wife may find out," prosecutors wrote in the motion.

Prosecutors also argued they should be allowed to respond to explanations presented by the defense about Farwell's conduct.

"The government has the burden of proof in this murder trial. With that burden, the government must be able to address with evidence the defendant's purported innocent explanations for his conduct. Now that Attorney Stevens has chosen to tell the jury that Farwell cheated on his wife and wore a mask to prevent her from finding out about it, the government should not be barred from introducing the evidence that directly rebuts those statements," prosecutors wrote.

Michael Coyne, NBC10 Boston's chief legal analyst, said prosecutors were trying to challenge the defense's explanation for the mask.

"They want to sort of dispel the narrative that he had any other reason to wear that mask other than to cover up his criminal activity," Michael Coyne said.

Coyne also discussed how images connected to the case could affect jurors.

"The video, the still photos of that, are very, very damaging. You can't look at those photos and think anything other than 'This looks like someone engaged in criminal activity.' And so the jury's going to see that over and over and over again," Michael Coyne said.

In another motion filed Sunday, prosecutors asked the judge to instruct jurors about what they called inaccurate legal statements and disputed exhibits mentioned by the defense during opening statements.

Farwell's defense has not filed a response to either prosecution motion, and the judge has not issued a ruling. Testimony was scheduled to begin Tuesday, with one early witness expected to be a Birchmore co-worker who contacted Canton police for a wellness check after she did not appear at work for several days.

The defense also argued Birchmore only told Farwell she planned to report the alleged abuse to his wife, while prosecutors said authorities could have learned about the allegations through other reports.

"As long as she was going to report those offenses, someone then — once she makes a report even to local authorities — could have then made the FBI aware of that," Michael Coyne said.