GAINESVILLE, Fla. -

Dr. Harry Krop is a well-known forensic psychologist who has probed the minds of some of this nation's most notorious criminals, including Gainesville serial killer Danny Rolling and the nation's first female serial killer, Aileen Wuornos.  Krop even spent time evaluating Casey Anthony, who was acquitted of killing her 2-year-old daughter. 

Now he's sitting down with Channel 4 to talk about the Cleveland sex captives, a case he calls the most unusual case he's seen in his career.

"I've done close to 3,000 first-degree murder cases," Krop said.

But for a man who's heard the worst of the worst in human behavior, Krop was intrigued when he heard the frantic 911 call from Amanda Berry, one of the three women held captive for nearly 10 years in Cleveland, and learned the women and a child had been rescued from a house of horrors.

"I have paid attention to this and it's been very interesting because it's most unusual," he said.

From a man who's heard the secrets of killers like Rolling and Wuornos, it says a lot.

Krop says forensic psychologists will be studying what happened in Cleveland for years to come, for three reasons.  First, the fact that these women are all alive.

"Usually we see with serial abductors, they may abduct more than one person but it's usually one person at a time and tragically the victims are usually killed," said Krop.

He says it's also out of the ordinary to see so many victims being held for so long.  Most victims of non-family abductions are tragically killed within the first 24 to 48 hours. 

"Is this about sex for this man or is it about power and control," I asked Dr. Krop. "All of the above," he said. "They have a need to control their victims to get their needs met at any time they want."

Krop says experts may one day determine Ariel Castro is a psychopath and a sadist.

"You look at this guy, if he is in fat guilty and you think, 'this is the everyday Joe, this is the guy living next door to all of us.' How does this happen, Dr. Krop?" I asked.

"Thats why they're psychopaths because they're very good at compartmentalizing," he responded. "I would predict, based on experience, that this guy had some history of abuse. I would expect that he derives from a fairly dysfunctional family unit. This is fairly common for psychopaths as well as sexual sadism."

As for the three women he allegedly subjected to that cruelty, Krop says the day they broke through that front door was just the beginning of the light at the end of the tunnel.

"So these women are extremely luck," I said. "They are.  Again that's not to say they're going to have an easy time of it," said Krop. "But I think through counseling they can be made into healthy females in the future.

By now, you've probably seen the compelling images of Ariel Castro's elderly mother crying, saying she's devastated by what happened and wanted to say "sorry" to the women who were held.

We don't yet know the type of environment her son was raised in, but Krop says all parents need to keep in mind, they need to model a healthy relationship for their children.  In his experience, people who turn to crime do so because of violence and abuse they've seen in their lives.