The revelation that one of Tori Stafford's killers has been transferred to a medium-security prison has sparked outrage from members of the slain girl's family, as well as Opposition MPs and many ordinary Canadians.

But moving prisoners from maximum to medium security, even murderers serving life sentences, is not uncommon in this country, experts say.

"At some point in somebody's sentence — even somebody who's sentenced for a horrific crime and serving a long or perhaps even a life sentence — it is not unusual for them to be moved down the security ladder," said Howard Sapers, the former correctional investigator of Canada, an ombudsman for federal offenders.

In a recent Facebook post, Rodney Stafford raged against the decision to transfer his daughter's rapist and killer, Michael Rafferty, from the maximum-security Port Cartier Institution in Quebec, asking: "Where in the world does it make sense that the worst of the worst of criminals ... even get the opportunity at a better life?"

Public Safety Minister Ralph Goodale said the Correctional Service of Canada is reviewing Rafferty's transfer to the medium-security La Macaza Institution, northwest of Montreal, back in March.

On April 8, 2009, Rafferty and his girlfriend, Terri-Lynne McClintic, abducted Tori Stafford off the street near her school in Woodstock, Ont. The eight-year-old's body was found three months later, buried under a pile of rocks in a field more than 100 kilometres north of her hometown.​

Rafferty was found guilty in May 2012 of kidnapping, sexually assaulting and murdering the little girl. He was sentenced to life imprisonment.

McClintic, who is also serving a life sentence, was recently returned to prison after her transfer to an Indigenous healing lodge also prompted widespread condemnation.

'Cascaded to medium security'

John Muise, a former member of the Parole Board of Canada, Ontario region, says he was among those critical of McClintic's transfer to the healing lodge. And while he certainly understands how upsetting Rafferty's transfer is for the Stafford family, he says it's fairly typical for someone serving a life sentence.

"If there's no institutional adjustment concerns, no escape concerns, they're usually cascaded to a medium-security institution," he said.

"There are hundreds, indeed thousands of people that have committed despicable crimes that are serving their sentences in medium-security institutions."

Tori Stafford's father is furious Rafferty was transferred to a medium-security prison. (Dave Chidley/Canadian Press)

According to Corrections Canada, 62.1 per cent of the nearly 14,000 federal inmates in this country were classified as a medium-security risk in 2016-2017.

The observations of institutional parole officers and security staff who interact with the inmates every day help determine their custody rating, and whether they belong in a maximum-, medium- or minimum-security facility.

An inmate's rating is based on his behaviour in prison, participation in correctional plans, escape attempts, alcohol and drug use, number of prior convictions and the severity of the offence that currently has him behind bars.

"All the decision-making that goes into [the rating] is a good one," Muise said.

"It's based on ... 'This is the offender. This is the offence. This is the criminal record. These are all the things we know about this fella. And so this is why we think it's safe [for him] to go here.'"

How do you prepare them?

Many inmates convicted of first- or second-degree murder will eventually be released, he said.

"So how do you prepare them for that?"

Muise suggests incarcerating criminals in maximum security for 25 years and then just releasing them may not be the best way to do it.

People aren't sent to prison for punishment. They are sent to prison as punishment. - Howard Sapers, former correctional investigator of Canada

A maximum-security institution is designed to house offenders who present a greater threat to the safety of the public, require a higher degree of supervision and/or have a higher chance of attempting to escape, according to Corrections Canada spokesperson Esther Mailhot.

Movement, association with other inmates and privileges are very restricted, she told CBC News in an email.

A medium-security institution has the same security safeguards as a maximum-security prison but allows for more interaction among offenders, she said.

Tori's father, Rodney Stafford, shared his thoughts about Rafferty's transfer in a recent Facebook post. The federal government is reviewing the transfer. (Hala Ghonaim/CBC)

Inmates in medium security might spend more hours out of their cell, and more time participating in group activities, but their freedom hasn't actually been increased as much as it may seem, said Sapers, who is Ontario's independent adviser on corrections reform.

"If you consider work a privilege or counselling a privilege or group therapy a privilege, then those are the kinds of things that you would typically have more opportunity to participate in," he said.

Sapers also pointed out that people in maximum security also qualify for family visits, and have some recreation and leisure time, just as people in medium security do.

Purpose of prison system

He said it's important for Canadians to understand the purpose of Canada's prison system.

'It may sound like a cliché, but people aren't sent to prison for punishment. They are sent to prison as punishment," he said. "That's an important distinction."

Despite what some Canadians may think, a maximum-security prison isn't meant to be a "more punitive" facility, but to afford more safety and security, Sapers said.