One key piece of evidence remains missing in the Victoria Stafford case.

Prosecuting a case without a body is rare but not unheard of, said one associate professor of law.

"It's not common but it has happened before," said Hamish Stewart, associate professor of law at the University of Toronto.

The 1990 disappearance of Elizabeth Bain was one high profile case where the accused, Robert Baltovich, was convicted without a body. Baltovich was acquitted of the murder last year. Bain's body has never been found.

"The Crown has to prove the accused killed the victim. Of course, that's easier with a body but it can also be done through circumstantial evidence, a confession or an eyewitness," said Stewart.

Police must have sufficient grounds to upgrade charges, he added.

It's uncommon but not impossible to prove murder without a body, said a law professor at the University of Western Ontario.

"Prosecutors will use other types of evidence to prove a person has been killed," said Sydney Usprich. "It could be an eyewitness who has seen the person being killed or other forensic evidence like blood or body parts."

A person's disappearance shows that something has happened, he added.

In the Stafford case, the public has not been told many details, but one of the accused, Terri-Lynne McClintic, has likely given information to investigators, said Usprich.

McClintic has assisted police in their investigation, her lawyer Jeanine LeRoy said last week. McClintic also accompanied police in searches for Tori's body in the Guelph area.