Farwell trial pivots to defense case as former boyfriend takes stand

The defense in the murder trial of former Stoughton police detective Matthew Farwell began presenting its case Wednesday, with key witnesses scheduled to testify Thursday. The shift in proceedings follows the prosecution's rest and centers on the mental state of Sandra Birchmore, who was 23 and pregnant when she died on Feb. 1, 2021. Farwell, 40, has pleaded not guilty to charges that he killed Birchmore and staged her body to appear as a suicide. He is also accused of causing the death of the male fetus she was carrying.

William Kilroy, 30, is expected to take the stand Thursday. He dated Birchmore around 2016 while they were students at Massasoit Community College. In a 2024 interview, Kilroy stated that Birchmore's mother and grandmother died within weeks of each other in 2016 and that the loss devastated her. He added that she used alcohol to self-medicate during that period. The defense plans to use his testimony to address a dispute between the couple that occurred in 2018.

According to Farwell's lawyers, Kilroy filed an affidavit on Jan. 22, 2018, claiming Birchmore threatened to kill herself and then blame him. Court records show a judge granted Kilroy a restraining order that day. The following day, Birchmore applied for and received a restraining order against Kilroy. Both orders were lifted the following month. The defense seeks to convince jurors that these events support their argument for acquittal.

Dr. Mindy Hull, the state’s chief medical examiner since 2017, is also expected to testify Thursday. Hull supervises Dr. María Del Mar Capó-Martínez, the forensic pathologist who performed Birchmore’s autopsy. In 2021, Capó-Martínez ruled the death a suicide. However, in April 2026, she withdrew that ruling and now classifies the manner of death as undetermined. Hull and Capó-Martínez met with federal prosecutors on Aug. 16, 2024, twelve days before the FBI arrested Farwell in a Revere parking lot.

That federal meeting included Dr. William Smock, an emergency medicine physician who reviewed the autopsy. Smock testified Tuesday that Birchmore could not have inflicted her own injuries given her age and the position in which her body was found. Capó-Martínez testified Monday that she relied on information available in 2021 to reach her initial suicide conclusion. She noted that state police investigators did not provide her with witness statements or inform her about the tens of thousands of text messages exchanged between Birchmore and Farwell.

The defense argues that Birchmore suffered from a long history of mental illness and had previously attempted suicide. They assert she was also concerned about her finances and the viability of her pregnancy. Farwell’s attorneys contend that Birchmore killed herself after he broke up with her and denied being the father of her child. DNA testing had excluded Farwell as the father of the fetus.

Joseph Harris, a Massasoit Community College administrator, was the first witness for the defense on Wednesday. He testified that Birchmore disclosed in December 2017 that she had threatened to kill herself over the previous weekend. Harris said the threat was made during a discussion about her tutoring hours. During cross-examination, Harris stated that the report was not considered an emergency and that such disclosures are common.

The trial is currently focused on whether Birchmore's death was a suicide or a homicide. The jury will hear from Kilroy and Hull to evaluate the defense's claims regarding her psychological state and the medical evidence. Farwell remains in custody while the defense continues to present its witnesses. The prosecution rested its case earlier this week, placing the burden of proof on the defense to raise reasonable doubt.