The bodies of a missing five-year-old Calgary boy and his grandparents have not been found, but that didn’t stop police from laying murder charges in the case.

It may seem unusual, but it’s not uncommon in Canada, according to one expert.  

“It’s a little bit unusual in a homicide investigation to have the charges laid prior to having bodies recovered, but it has happened in several cases across this country,” Dave Perry, the CEO  of Investigative Solutions Network, told CTV’s Canada AM Tuesday.

In most cases, all police need to lay the charges is what’s called “reasonable grounds,” Perry said. That’s a “low threshold,” but the case of the missing Calgary family is high-profile and investigators must have strong evidence to support the charges, he added.

In another well-publicized case, two suspects were arrested and charged with the abduction and murder of eight-year-old Tori Stafford two months before her remains were discovered in a secluded Ontario field.

In the Calgary case of five-year-old Nathan O’Brien and his grandparents, Kathryn and Alvin Liknes, police are “not going to take (murder charges) lightly,” Perry said.

“Clearly, they’ve got some strong evidence.”

Perry said the Calgary investigators are likely relying on forensic evidence, which may have been collected at the Liknes family home.

Police have said that a violent crime appeared to have taken place at the home, so investigators may have picked up some DNA evidence, Perry said.

Nathan was staying with his grandparents for a sleepover when the three family members were last seen on June 29. When his mother came to pick him up the next day, they were all gone.

Calgary police have said that they are optimistic the bodies will be found so that the O’Brien and Liknes families can have some closure.

A community effort is underway to search rural areas near Airdrie, Alta., in connection with the case. Police are also asking property owners to notify them if they see anything suspicious.

Douglas Garland, 54, has been charged with two counts of first-degree murder and one count of second-degree murder.