BELLEVILLE, Ont. -  Lurid details of the self-professed double life of Col. Russell Williams are expected to be brought before the public starting Monday when the former rising star in the Canadian military is scheduled to plead guilty to murdering two women, sexual assaults and a slew of other criminal charges.

Williams, 47, was the commander of the country's largest military airfield, CFB Trenton, until he was arrested in February and charged in the deaths of Jessica Lloyd, 27, and Cpl. Marie-France Comeau, 38.

The arrest, which shook Canada's military to its core, left many unanswered questions. Did the high-ranking officer who flew the Queen and the prime minister around the country harbour disturbing sexual fantasies that eventually led to assault and murder? And how could someone hide such a dark secret?

The stark contrast between the two images -- that of a seemingly "well-adjusted," successful military man and an alleged depraved sexual predator -- has drawn intense public attention to the case, said Adam Boni, a Toronto criminal lawyer who has co-authored a legal text on sentencing.

"This is the type of case that we simply haven't seen in Canada before," said Boni, who served as a federal prosecutor before switching to defence a decade ago.

"I say that because this gentleman (allegedly) lived such an incredible double life, it's almost a 'Jekyll and Hyde' type of case. It's the deepest, darkest fear that each and every one of us has about the neighbour down the street, or the teacher at school, or the seemingly normal business professional walking down the street."

Earlier this month a lawyer for Williams told the court his client would plead guilty to all charges -- two counts of first-degree murder, two counts of sexual assault, two of forcible confinement and 82 break-and-enter charges dating back to 2007, some of which involved lingerie.

He faces an automatic sentence of life in prison with no possibility of parole for at least 25 years.

Boni said it is rare for accused persons to announce their intention to plead guilty at a later date. In this case, he said, it was clearly a step taken to assure the public, the military, the families of the victims and the survivors that they wouldn't be put through the "emotional torture" of a trial.

"The allegations in this case would appear to be so lurid, so disturbing that a trial in this case would probably have changed the Trenton community for the rest of its existence," Boni said.

"It would have had a thunderous impact on the local community and it would have had a devastating impact on the victims and their families."

Monday's guilty plea will be followed by a sentencing hearing at which victim impact statements will be presented to the court. The hearing is expected to last several days.

Investigators reportedly have a nine-hour video statement that Williams gave to police and videos he allegedly made of parts of the rapes and murders. The published report is unconfirmed and it is not yet clear what evidence will be entered into the public record following the guilty plea.

Comeau was found dead in her home in Brighton, Ont., last November. She was a flight attendant at CFB Trenton and served aboard the same military VIP flights Williams piloted for much of the 1990s, ferrying the Governor General and other dignitaries on domestic and overseas trips.

Williams is alleged to have burglarized Comeau's home 10 days before she was found dead on Nov. 25, but court documents don't specify what was allegedly stolen.

Lloyd was found dumped on a dirt road in nearby Tweed, where Williams lived. She worked in Napanee, Ont., co-ordinating school bus schedules.

Before his arrest, police had been looking for a suspect in two home invasions near Williams' house in eastern Ontario in which women were tied up and sexually assaulted. Police initially focused on one neighbourhood resident.

Some of the break-and-enter charges centre around the Ottawa neighbourhood where Williams once lived. A man whose house was among those burglarized said he and his wife came home one day to find family pictures on their bed and the underwear drawers of his wife and daughters left open.

One of Williams' alleged sex assault victims, who has launched a lawsuit, claims a "horrific and reprehensible" sexual attack has left her fearful and suicidal. The allegations have not been proven in court.

Alasdair Goodwill, a forensic psychologist and professor at Ryerson University, said it's hard to say what may have led to the break-ins without knowing Williams' history.

Generally, some offenders may break into homes for reasons beyond simply stealing items. In this case he may have felt a sense of power over the victims in doing so, he said.

Stealing personal items, such as underwear in a burglary, may also be an attempt to sexualize and make intimate what is typically a rather benign impersonal offence.

Such offenders have a sexual preoccupation and are often driven by feelings of inadequacy that they may try to mask by becoming high achievers in their public lives, Goodwill said.

Some can maintain a double life, committing their crimes much like they live their normal lives, by being organized and planning ahead, he said.

But some sexual offenders continue to push the boundaries until their behaviour escalates to violence, he said. It's similar to a drug addict who needs a "little bit more each time" to experience the same feeling.

"Whether he stays in the house a little bit longer now, whether he steals more objects, something has to escalate in some way maybe to get the same thrill that he was having originally," Goodwill said.

The other possibility is that something triggered the violence, such as someone catching the offender in the act of breaking into the home, he added.

Based on what he's read about the case, Goodwill said he believes Williams was "clearly at a very high risk of committing further offences" had he not been caught. Police did an "extraordinarily good job" in apprehending him, which may have saved other women.

Although some have compared Williams's case to that of convicted schoolgirl sex killer Paul Bernardo, the two cases are very different, said Boni.

Unlike Bernardo, Williams apparently didn't come from a dysfunctional family and had the kind of "meteoric" career and disciplined personal life that Bernardo never did, Boni said.

"We are catching a glimpse at someone who I think we will very rarely see again," Boni said.

"The duality in this individual's public and private persona is quite remarkable, both from a public interest perspective and a psychological and psychiatric perspective."