A former Massachusetts police detective has been found guilty of murdering a young pregnant woman prosecutors say he had been grooming since she was a teenager.

Matthew Farwell, a former Stoughton Police Department detective, was convicted of killing Sandra Birchmore inside her Canton apartment in February 2021. Investigators say he staged the scene to make her death appear to be a suicide.

The U.S. Attorney for Massachusetts confirmed Farwell was found guilty on Tuesday of murdering Birchmore and causing the death of her unborn child. Jurors began deliberating Friday after hearing more than three weeks of testimony in the federal murder trial.

FORMER MASSACHUSETTS POLICE OFFICER FACES MURDER TRIAL OVER PREGNANT WOMAN’S STAGED SUICIDE

Farwell had been charged with killing a witness or victim and causing the death of an unborn child.

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Prosecutors said Farwell killed Birchmore after she became pregnant and threatened to expose their years-long relationship, which they say started when he began grooming her when she was just 15 years old and he was 27.

FORMER MASSACHUSETTS POLICE OFFICER FACES MURDER TRIAL OVER PREGNANT WOMAN’S STAGED SUICIDE

Sandra Birchmore pictured in a selfie she posted to Facebook in January 2021, about three weeks before she was killed in a scene prosecutors allege was staged to look like a suicide. Former Stoughton Police Officer Matthew Farwell has been accused of killing her and her unborn child. (Sandra Birchmore/Facebook)

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Birchmore was found dead with a strap around her neck inside her apartment. Her death was initially ruled a suicide, but the medical examiner later changed the official manner of death to undetermined.

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Federal investigators eventually reopened the case, uncovering approximately 40,000 text messages between Birchmore and Farwell and evidence prosecutors said pointed to a yearslong sexual relationship.

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Matthew Farwell, a former Stoughton, Mass., police officer, pleaded not guilty Wednesday, Aug. 28, 2024, to charges of killing a woman he is accused of sexually exploiting when she was underage. (Stoughton Police Department via AP)

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During closing arguments, prosecutors portrayed Farwell as a former police officer who feared Birchmore would expose his alleged misconduct.

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Meanwhile, Farwell’s defense argued Birchmore died by suicide and pointed to her history of mental health struggles and previous suicidal statements. Farwell’s attorneys acknowledged the extramarital relationship but maintained he did not kill her.

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A defense medical expert also disputed the prosecution’s conclusion that Birchmore had been strangled.

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Farwell faces mandatory life imprisonment without the possibility of parole.