Charges of criminal negligence causing the death of Ashley Smith of Moncton have been dropped against three guards and one supervisor at the Grand Valley Institution for Women in Kitchener, Ont.

Smith, 19, had been in detention since she was 16 years old. She died on Oct. 19, 2007, of "self-initiated" asphyxiation.

In a Kitchener courtroom Monday, the Crown said new medical opinions found the four prison employees could not have reached Smith in time to save her life. Therefore, the charges were dropped.

The decision to drop the charges came two-thirds of the way through a three-week preliminary hearing to decide if there was enough evidence to send the matter to trial.

Jason Godin, the Ontario regional president of the Union of Canadian Correctional Officers, said the charges should never have been laid in the first place.

"We’re obviously extremely pleased with that decision. Like we’ve said since the very beginning, our members are guilty of absolutely nothing. They were put in a completely impossible situation," he said.

The union said Smith had a history of self-mutilation and tried almost daily to choke herself.

Godin said Correctional Service Canada managers ordered guards to wait until Smith stopped breathing before trying to help her. He said he hopes this case will force the prison system to review how it treats women prisoners.

"We need to take a serious look at how federally sentenced women’s facilities are managed across the country. Clearly, in our minds, there needs to be major reforms," Godin said.

The union said Smith spent most of her time in jail in segregation without access to programs.

Godin said he wants a public inquiry to prevent what happened to Smith from happening to other female prisoners. He also wants Correctional Service Canada to rehire the three guards who were fired after being charged in this case.

"They have to own up to their responsibility in this situation, and they have to do what’s right in terms of reinstating our members," he said.

Former guards Karen Eves, Blaine Phibbs, Valentino Burnett and supervisor Travis McDonald were all charged with criminal negligence causing death.

Along with four other employees, they were suspended after Smith's death pending an internal investigation by Correctional Service Canada. The four, along with two managers, were later fired.