Drunk driving charges have been stayed against a a woman because a judge says her charter rights were violated while she was in prison.

Stephanie Mok was arrested in January 2010 when she was stopped with three times the legal blood alcohol level.

Mok used the toilet twice that night in a cell without knowing she was being observed through a surveillance camera.

Police say surveillance is used for officer and prisoner safety and there is no policy that requires an officer of the same sex to watch a prisoner.

The judge, though, says the monitoring and videotaping of detainees of the opposite sex is highly intrusive and an invasion of privacy.

Legal expert James Morton says he doesn't see an issue with surveillance when officers are of the same gender. 

"People hang themselves in prison, people cause problems," Morton says. "It makes sense to have some type of supervision but you can narrow that to people of the same gender."

He says what's interesting about this case is that the judge went as far as staying the charges.

"That's where the case is subject perhaps to a good appeal. Staying a charge is something that you do only in the most extreme circumstances," Morton says. "That having been said, my sense is that Justice [Peter] West's report says, if I don't do something like this, I just make a comment saying this is improper, that's going to go nowhere."