The medical examiner who first ruled Sandra Birchmore’s death a suicide told jurors Monday that she made that call with limited information from police, and that she was told nothing about evidence pointing to a homicide. Later in the day, Matthew Farwell’s twin brother, former Stoughton police officer William Farwell, took the stand under a grant of immunity and testified that he, too, had a sexual relationship with Birchmore, including while he was on duty.
Monday, October 26, 2026, was the tenth day of testimony in United States v. Farwell in federal court in Boston, reported by NBC10 Boston, 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.
The medical examiner
- The first ruling. Dr. Maria Del Mar Capo Martinez performed the 2021 autopsy and initially ruled the death a suicide, with the cause “asphyxia by hanging.” She testified that she had limited information from police at the time, 7News reported. Canton police found Birchmore on February 4, 2021, with a strap around her neck tied to a doorknob, according to 7News.
- How investigations shape the ruling. Over defense objections, prosecutors asked whether the quality of a police investigation can affect her decision on manner of death. “It can affect the way we do the manner, because we are dependent on other agencies to provide information,” she said, as reported by 7News.
- What she was not told. She said she was given no information about evidence that the death could have been a homicide. Asked about a necklace found broken on the front of Birchmore’s body, which prosecutors say is evidence of a struggle, she said, “At the time of the examination, I did not have any information regarding the necklace,” according to 7News. She also testified that a mark on Birchmore’s chin could be an abrasion, though she did not note it in her autopsy.
- The police reports. Jurors heard about a Canton police report that described a scarf around Birchmore’s neck and a State Police report she reviewed with the header “Birchmore suicide,” 7News reported.
- The change. Birchmore’s death certificate was later amended to list the cause as asphyxia and the manner as undetermined. NBC10 reported that she said she consulted colleagues before making that change.
The cross-examination of the medical examiner
The defense focused on how the ruling changed and who was involved, according to NBC10’s account:
- The original certificate. The defense put Birchmore’s original death certificate, listing suicide, into evidence.
- The meeting. The defense asked about a meeting about three years after the autopsy that included her office, the chief medical examiner, the U.S. Attorney’s Office, the FBI and the State Police. She said neither she nor her office called it, and that she had never attended a meeting with all of those groups at once.
- Information from prosecutors. She testified that she received packets of information from the U.S. Attorney’s Office. The defense sought to show she had also been told of other information, including that Birchmore once took a handful of pills after an argument with her mother. Many of the defense’s follow-up questions on that subject drew sustained objections.
- The hyoid bone. She agreed that hyoid bones do break in younger people and in partially suspended hangings. On redirect, she said she could not recall seeing a fractured hyoid in a person under 30 in a seated position, and that there were no signs of new or old cutting on Birchmore’s body.
- What she did not know. She said she had no information about whose DNA was on the ligature or who had a key to the apartment. She also testified that she does not work for either side.
The therapist finishes
Diala Alkhalil, the mental health counselor who treated Birchmore on and off since childhood, completed her testimony Monday. She said Birchmore was excited to become a mother, never appeared suicidal, and was upbeat the day before her death, and that she called police to raise concerns about foul play after hearing the death was ruled a suicide, 7News reported. Boston 25 reported that when the defense asked whether Birchmore’s account of seeing her late mother at the foot of her bed holding her unborn baby could have been a hallucination, Alkhalil said she did not endorse the account but respected Birchmore’s beliefs and did not classify it as a hallucination.
William Farwell testifies under immunity
- The immunity. William Farwell confirmed he was testifying under a grant of immunity. NBC10 reported that he said he was concerned about being charged for having sexual relations while on duty.
- The relationship. Prosecutor Brian Fogarty asked, “Did you ever engage in sexual contact with Miss Birchmore while you were on duty as a Stoughton police officer?” according to 7News. He testified that the relationship began in 2018, when Birchmore was 20 or 21, after she sent him an unsolicited Facebook message while he was working a detail asking whether she could bring him anything.
- Before she was 18. He said he did not recall interacting with Birchmore before she was 18, NBC10 reported.
- What he knew about his brother. Asked what he knew about Matthew Farwell having sex with Birchmore in July 2018, he answered, “In July 2018, I had no knowledge,” according to 7News.
Testimony ended for the day with William Farwell still on the stand. He returned Tuesday.
What witness immunity means in federal court
A witness can refuse to answer questions that might incriminate him. Federal law gives prosecutors a way around that refusal:
- The order. Under 18 U.S.C. § 6003, a U.S. Attorney, with approval from senior Justice Department officials, can ask the district court for an order requiring a witness to testify when the testimony “may be necessary to the public interest” and the witness has refused or is likely to refuse on Fifth Amendment grounds.
- The protection. Under 18 U.S.C. § 6002, once the order issues, the witness cannot refuse to testify, but “no testimony or other information compelled under the order (or any information directly or indirectly derived from such testimony or other information) may be used against the witness in any criminal case.”
- The exception. The protection does not cover “a prosecution for perjury, giving a false statement, or otherwise failing to comply with the order.” A witness who lies on the stand can still be charged for the lie.
The statute protects the witness from use of his own words. It does not by its terms bar a prosecution based on evidence obtained independently. The public reports do not describe the terms of William Farwell’s immunity beyond his confirmation that he received it.
What comes next
William Farwell resumed testifying Tuesday, October 27. Prosecutors have said they could rest this week, NBC10 reported, and Boston 25 reported that closing arguments could begin in the first week of November.
Frequently asked questions
What did the medical examiner say at the Farwell trial?
Dr. Maria Del Mar Capo Martinez testified on October 26, 2026 that she first ruled Sandra Birchmore’s death a suicide with limited information from police and was told nothing about evidence of a possible homicide, including a broken necklace. The death certificate was later amended to list the manner of death as undetermined. On cross-examination, the defense focused on the original certificate and a later meeting with prosecutors and investigators.
Why did William Farwell get immunity?
He testified that he was concerned about being charged for having sexual relations with Birchmore while on duty. Under federal law, testimony compelled under an immunity order cannot be used against the witness in a criminal case, except a prosecution for perjury or false statements.
Did William Farwell know about his brother’s relationship with Birchmore?
Asked what he knew about Matthew Farwell having sex with Birchmore in July 2018, he testified, “In July 2018, I had no knowledge.” His testimony continued on October 27.
Sources: NBC10 Boston, 7News (WHDH) and Boston 25 News, October 26 and 27, 2026. 18 U.S.C. §§ 6002 and 6003 read at Cornell’s Legal Information Institute. Matthew Farwell has pleaded not guilty and is presumed innocent. General information, not legal advice.