MONTREAL - It can be remarkably easy to make people confess to murder. Interrogation experts say the key is finding a cold-blooded killer's sensitive spot.

Enlarge Photo THE CANADIAN PRESS/HOCol. Russell Williams is shown in this court-released image from his interrrogation by police captured on video and shown Wednesday in a Belleville, Ont. courtroom. Williams told police that while he did ask himself why he raped and killed women he could never come up with an answer and he was “pretty sure the answers don't matter.” Identifying something the suspect holds dear, such as a photo of a grandchild or a beloved pet, can make someone spill their darkest secrets.

In the case of Col. Russell Williams, he began to unravel when police said they were searching the Ottawa home treasured by his wife.

His gum-chewing grin disappeared as he fretted about whether police might ransack the residence.

"I’m struggling with how upset my wife is right now," Williams told Ontario Provincial Police investigators, adding later, "I’m concerned that they’re tearing apart my wife’s brand new house."

Williams' cool demeanour melted away. His arms folded across his chest. His head slumped downward. And the wisecracking tone was replaced by a monotonous near-whisper.

The interview was shown Wednesday in a Belleville, Ont., court where Williams pleaded guilty to more than 80 charges, including two horrific sex murders.

It's been described as textbook police work.

Outside court, a senior police officer characterized the 10-hour interrogation as one of the best interviews he has ever seen.

"It's a smart man, outsmarted by a smarter man," said Det. Insp. Chris Nicholas.

While movies and television portray a cat-and-mouse game between murderers and cops in the interrogation room, real life is usually different.

It can actually be surprisingly simple.

"What most people don't know is it's easier to get a confession for homicide than it is for a break-and-entry or another minor crime," said Steve Roberts, a retired homicide investigator with the Montreal police.

"The key is to find what his weakness is and use it."

He said committing a murder usually brings a burden of guilt that is harder to grapple with than, for example, stealing a neighbour's hub caps.

The first thing a suspect often asks for after a confession is food because, Roberts says, their guilt has made it impossible to eat for days.

Elliott Leyton, a university professor who has written landmark studies on serial killers, said sometimes they volunteer their confessions and sometimes they hold out to the last minute.

Meanwhile, the interrogator can lay down his cards, one piece of incriminating evidence at a time.

Williams "is intelligent enough to know that they had him," said Leyton, who is an anthropology professor at Memorial University in St. John's, NL.

"He didn't want any more public shaming than he could avoid, I assume, and therefore he made a decision to bail out now, avoid the trial, avoid the public shaming, avoid the whole excruciating process of humiliation that was set up for him."

He said most cases are resolved after interrogations. He cited Ted Bundy, a U.S. serial sex murderer who eventually confessed to 30 murders committed in the 1970s after intense interrogation.

Roberts said that preparation is key before going into an interrogation room.

He said that while a suspect cools his heels in a cell, officers will go search his home and effects, often keying in on what's important to him, anything that can be exploited as a weakness.

"We cracked a guy from the Hells Angels because in his wallet were pictures of his dog and his dog was the most important thing in his life," Roberts said, explaining he established a rapport with the biker as a fellow dog lover.

"You get him talking," he said. "There's a buildup of trust and he'll tell you the story."

And, hard as it might be, the veteran police officer said a good interrogator isn't judgmental.

"You have to try to understand why the guy did this," said Roberts, who was a police officer for 34 years, 10 of them as a homicide detective in the force's elite major-crimes unit.

"You don't go for speed. Everybody has their time and it depends on you talking. You've got to be a good talker but you've got to be a better listener."

Laying out the evidence can be key.

He said serial killer William Fyfe, who was convicted in 2000 of killing five Quebec women, would recount his crimes if he saw police had the evidence.

"He could describe it to the minute detail, as if he was performing it right there then," Roberts said.

But he wouldn't bite if police went fishing for information on a murder.

"He'd shrug his shoulders. He'd just smile at you."

He said Montreal police went to video declarations over written statements because it was found judges and juries had a hard time believing people would actually admit to murder.

"They could see that we never made any promises and that the guy really wanted to tell the story."

Ultimately, Roberts said, there is one other key element detectives remember when they sit down across from a suspect — the victim.

"You're doing it for the family," he said.