The former Stoughton cop who allegedly sexually exploited a teenage volunteer at the department for years and then killed her after she became pregnant has asked to remain in detention voluntarily, canceling an upcoming hearing.

Former Stoughton Police Detective Matthew Farwell, 38, is accused of of strangling three months-pregnant Sandra Birchmore, 23, and staging her body to look like a suicide in her Canton apartment in 2021. Farwell was indicted by a grand jury for Birchmore’s murder and arrested in late August. He pleaded not guilty.

The federal judge granted Farwell’s motion for voluntary order of detention on Monday, allowing him to remain in custody and canceling a hearing on the case scheduled for Thursday. Under the order, Farwell retains the right to request a detention hearing at a later date.

Prosecutors allege Farwell groomed Birchmore from the time she joined the department’s Police Explorers Academy in 2010 at age 12. She remained in the program for four years, and Farwell allegedly began to rape her when she was 15 and he was 27.

The abuse and sexual exploitation allegedly continued for seven years, the indictment stated, during which Farwell got married and had a child. As an adult, Birchmore, an aspiring nurse, became interested in having a child, and prosecutors stated Farwell agreed to try to impregnate her in return for her silence.

In December of 2020, prosecutors said, Birchmore learned she was pregnant. Court documents state during the pregnancy, the cop’s physical abuse escalated, Birchmore composed an apparently-unsent text disclosing their relationship to his wife, and the victim’s friend called the Stoughton Police to report Farwell.

An unknown employee with the police department told Farwell of the report, prosecutors allege, leading him to confront and allegedly strangle Birchmore.

The Office of the Chief Medical Examiner initially ruled the victim’s death a suicide, but the prosecution stated they retained an expert who disagreed with the finding.

In August, Acting U.S. Attorney for Massachusetts Joshua Levy did not state whether any other officers or individuals may be charged in connection to Birchmore’s death but said the investigation remained open.

Farwell faces a mandatory life sentence if found guilty and may face the death penalty, according the Levy.

Farwell is scheduled to return to court for a status conference on Oct. 17.