BOSTON (WHDH) - In day five of testimony in the Matthew Farwell murder trial, an FBI special agent testified about text message exchanges between the former Stoughton police officer and Sandra Birchmore, the 23-year-old he is on trial for killing.

Farwell is charged with killing 23-year-old Birchmore and her unborn child and staging the death to look like a suicide. Prosecutors allege Farwell killed her to stop her from exposing federal crimes, including sexual exploitation of a child. They claim Farwell had been grooming her for sex since she was 15-years-old and part of the Stoughton Police Explorers mentoring program.

FBI Special Agent Heidi Kelsch read texts between the two in court Monday, testifying that the pair argued frequently in the months leading up to her February 2021 death.

Kelsch told the jury that Birchmore texted Farwell six years ago about an arrangement in which he would help her get pregnant and she wouldn’t reveal who the father was.

Birchmore’s text read:

“I will keep my word to you. This isn’t something I would ever go back on. […] You won’t regret this. You’ll be proud of me as a mom to your kid.”

Prosecutors said Farwell eventually became concerned that Birchmore was changing the terms of their deal after she later wanted him to sign the baby’s birth certificate and be present for the birth.

A text from Farwell in response read:

“It’s a lot to think about, and so much more than you have ever asked for.”

Kelsch testified that Birchmore told a friend Farwell would often grab her phone from her, and become aggressive. In one December 2020 exchange, Farwell texted Birchmore saying “Having you in my life has (expletive) me over and over again. […] You blackmailed me into getting what you wanted.”

During that conversation, Birchmore spoke about harming herself, saying:

“I wish I was never born – everyone’s lives would be better for never having known me.”

Kelsch said Birchmore did not make web searches or write journal entries about suicide.

In texts Birchmore to friends, she indicated she was pleasantly surprised Farwell was suddenly nicer to her in the days before she died.

The jury is aware that Farwell is not the father of Birchmore’s unborn child.

Farwell’s defense maintains that Birchmore took her own life.

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