Matthew Farwell’s twin brother told jurors Tuesday that Sandra Birchmore texted him that her sexual relationship with his brother began “when I was 15,” and that he did not believe her because he “didn’t think my brother was that dumb.” Later in the day, a prosecution expert, Dr. William Smock, testified that Birchmore “was the victim of a homicidal act” and that investigators had walked into an altered crime scene.
Tuesday, October 27, 2026, was the eleventh day of testimony in United States v. Farwell in federal court in Boston, reported by WBUR, 7News (WHDH) and Boston 25 News. Farwell, a former Stoughton detective, is charged with killing Birchmore and her unborn child in February 2021 to keep her from exposing their sexual relationship, which prosecutors say began when she was 15 and in the department’s Explorers program. He has pleaded not guilty. His defense says Birchmore died by suicide in her Canton apartment after Farwell ended their relationship.
William Farwell’s second day on the stand
Former Stoughton police officer William Farwell testified over two days under a grant of immunity. He told the jury he sought immunity because he had sex with Birchmore, when she was around 20, while he was on duty as a Stoughton officer, WBUR reported. He said both brothers had sex with her but never discussed it with each other while she was alive.
- The “I was 15” text. In text messages shown in court, William Farwell asked Birchmore when her relationship with his brother started. “Like when I was 15,” she wrote. He replied, “Nice,” WBUR reported. He explained, “The first reason was I didn’t necessarily believe her, and the second was I didn’t think my brother was that dumb,” according to 7News.
- The phone call. He testified that in a 2021 phone call he asked his brother to tell him he had not had sex with Birchmore when she was under 16, and that Matthew Farwell said he had not, WBUR reported.
- The pregnancy. He said Birchmore told him in person that she was pregnant with his brother’s child. He told her, “You two need to figure this (expletive) out. This is a horrible idea. To be honest, I can’t or won’t be in the middle of it,” according to 7News. Asked about her mood, he said “she seemed happy,” that she planned to go back to school, and that he did not observe a “desire for her to hurt herself,” WBUR reported.
- The meeting with investigators. Boston 25 News reported that William Farwell testified that, after Birchmore’s death, State Police Sgt. John Fanning and Trooper Matthew Dunne of the Norfolk County State Police detective unit met with him in his truck and told him he was not a suspect. He testified that Fanning said, “We’re getting a lot of calls, and we need to get this closed out,” according to Boston 25.
- What his brother told him. After that meeting, he testified, Matthew Farwell told him he had wiped his cell phones and that the investigation was wrapping up, Boston 25 reported. “He said there could have been criminal charges, but it’s not a victimless crime,” William Farwell testified.
The cross-examination
The defense tried to discredit him. Lawyers asked about his own affair with Birchmore and suggested he blamed his brother for the loss of his job; he resigned from the Stoughton department in 2022 during the investigation into her death. “I am not upset with my brother about that,” he said, according to WBUR. Boston 25 reported that the defense asked whether he had wanted to end his relationship with Birchmore but “felt trapped,” so continued to see her. William Farwell is also a defendant in a civil lawsuit brought by Birchmore’s estate and her aunt, Darlene Smith, which is on hold during the criminal trial, WBUR reported.
Dr. William Smock: “a homicidal act”
Smock, whom WBUR described as a police surgeon and former emergency medicine physician, reviewed the autopsy and crime scene photos for the prosecution. He did not examine Birchmore’s body; the state medical examiner, Dr. Maria Del Mar Capo Martinez, is the only expert who did, according to WBUR.
- His conclusion. “Ms. Birchmore was the victim of a homicidal act,” he told jurors. He said the cause of death was asphyxia related to strangulation and the manner was homicide, and that “this is an altered crime scene and that she was killed before the ligature was tied around the door,” Boston 25 reported.
- The hyoid bone. He testified the hyoid bone in her neck was fractured inward on the right side while her neck was tilted to the left, which he said was not consistent with a partial hanging. “This is consistent with a strangulation where the bone is squeezed inward,” he said, according to Boston 25.
- The clasp mark. He said a red imprint on her upper right chest was made by a clasp on the strap, but that the clasp was tied around the doorknob when she was found, which told him the injury happened before the strap was tied to the door, Boston 25 reported.
- Hair, a scratch and the necklace. He called Birchmore’s hair tangled in the strap a “huge red flag for a forensic investigator,” WBUR reported. 7News reported that he described a defensive scratch in crime scene photos and marks he said showed her clinging to the strap and trying to free her nose and mouth, and said a broken necklace under the strap, which state and local investigators did not find, is something he has never seen in a suicide.
- Cross-examination. The defense attacked his credentials, pointing out that he is not a board-certified forensic pathologist, WBUR reported.
More from the medical examiner
WBUR’s account of Monday’s testimony added detail on how the death certificate changed. Capo Martinez ruled the death a suicide by “asphyxia by hanging” in 2021 and changed it in April 2026 to “asphyxia,” manner “undetermined.” She confirmed that Smock told her his theory at a 2024 meeting with FBI investigators, before she made the change. Asked by prosecutors, she said she was “not pressured.” She said she had changed a death certificate only once or twice in 10 years: “We don’t take that lightly.” On cross-examination she agreed it was possible that Birchmore’s head resting on her chest for several days could have affected the hyoid bone; Birchmore was found three days after she died.
Why an expert who is not a forensic pathologist can testify
Federal Rule of Evidence 702 lets a witness “qualified as an expert by knowledge, skill, experience, training, or education” give an opinion if the party offering it shows the judge that it is “more likely than not” that:
- the expert’s specialized knowledge “will help the trier of fact to understand the evidence or to determine a fact in issue”;
- the testimony “is based on sufficient facts or data”;
- it “is the product of reliable principles and methods”; and
- the opinion “reflects a reliable application of the principles and methods to the facts of the case.”
The rule does not require any particular board certification; experience and training can qualify a witness. Once a judge admits the testimony, the fight over credentials moves to the jury. In Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993), the Supreme Court wrote that “vigorous cross-examination, presentation of contrary evidence, and careful instruction on the burden of proof are the traditional and appropriate means of attacking shaky but admissible evidence.” That is what the defense did Tuesday: it challenged Smock’s qualifications in front of the jurors, who decide how much weight his opinion deserves.
What comes next
Prosecutors were expected to call two final witnesses and rest their case Wednesday, October 28, after which the defense would begin calling witnesses, Boston 25 reported. Closing arguments could begin in the first week of November.
Frequently asked questions
What did William Farwell say about the “I was 15” text?
He testified that Birchmore texted him that her relationship with his brother began “when I was 15,” that he replied “Nice,” and that he did not believe her and “didn’t think my brother was that dumb.” He testified under a grant of immunity on October 26 and 27, 2026.
Who is Dr. William Smock?
A prosecution expert whom WBUR described as a police surgeon and former emergency medicine physician. He testified on October 27, 2026 that Birchmore died of asphyxia related to strangulation, that the manner of death was homicide, and that the scene had been altered. The defense noted he is not a board-certified forensic pathologist.
When will the defense present its case in the Farwell trial?
Prosecutors were expected to rest on Wednesday, October 28, 2026, with the defense beginning its case after that.
Sources: WBUR, October 27, 2026; 7News (WHDH), October 27, 2026; Boston 25 News, October 27 and 28, 2026. Federal Rule of Evidence 702 read at Cornell’s Legal Information Institute; Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993), read on CourtListener. Matthew Farwell has pleaded not guilty and is presumed innocent. General information, not legal advice.