A nine-months pregnant teenager has been placed behind bars in a Toronto-area jail to ensure she testifies against her boyfriend after lodging a domestic violence complaint against him. 

Noelly Mowatt, 19, doesn't face any criminal charges but for nearly a week she's been held at the Women's Centre in Milton, a provincial jail near Toronto.

A judge ordered her to be placed in jail on a material witness warrant after the Crown prosecutors in her boyfriend's case expressed concerns she wouldn't testify at his trial.

The warrant was issued after police said they tried several times to serve her with a subpoena to attend court.

Mowatt is expected to be released after she testifies at her boyfriend's trial on Friday. Christopher Harbin, 25, is facing eight charges, including assault and forcible confinement.

But her lawyer says Mowatt's due date is early next week and she's worried she may give birth while in custody.

"This is an outrage. It's totally unjust," lawyer Lydia Riva said on Tuesday.

Riva said such warrants are usually used to make street gang members testify, and she's never heard of it being used for a victim of alleged domestic violence.

Women's groups say they are worried the case may deter other domestic violence victims from reporting such crimes.

"It's a really difficult decision to pick up the phone and call the police on your spouse," said Leslie Ackrill, manager of Interval House, a shelter for battered women.

"It's one of the things that so many women fear because they fear retaliation from their spouse. And now they're going to fear retaliation from the authorities."

But Susan Chapman, who spent 16 years as a Crown prosecutor and now teaches law, says sometimes Crown prosecutors are required to pursue domestic violence at the expense of a victim's autonomy.

"The problem with autonomy is you're giving the power over to the victim in the case in what is really a public prosecution," she said. "And then you can make that woman vulnerable to intimidation and further abuse by the perpetrator."