How were the Cleveland women held captive for so long?

Law enforcement and psychology experts looking at the Cleveland abduction case say it was likely a combination of intimidation, luck and so-called "Stockholm syndrome" that made it possible for three women to be held captive for a decade.

• Cleveland missing women were bound, chains found in home
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On Monday night, Cleveland police rescued Amanda Berry, Gina DeJesus and Michelle Knight, who had all been missing since the early 2000s, from a house near downtown Cleveland.

Police charged the owner of the home, Ariel Castro, 52, with four counts of kidnapping and three counts of rape.Police and prosecutors now say there is nothing to leadthem to believe Ariel Castro's brothers Pedro, 54, and Onil, 50, were involved in or had any knowledge of the alleged crimes.

Marlene Dalley, who worked in the RCMPs National Missing Children's Services program for 25 years, says theres an assumption that all abductors match the same psychological profile. But Dalley says its the circumstances of each case that determine the outcome.

Individuals "who keep people in captivity do not necessarily fit a certain profile," Dalley says. "These cases all have unique characteristics."

The Cleveland case has prompted the question of how someone could kidnap and conceal three women in a crowded residential neighbourhood for a decade without raising suspicion.

Homeowner seemed average

One of Ariel Castros neighbours, Charles Ramsey, called 911 on Monday night after seeing a woman, who turned out to be Amanda Berry, screaming and trying to escape through the front door of the house.

• Photos of the Cleveland missing women case

Ramsey told a reporter from WEWS-TV that he had barbecued with Castro in the past, and said he didnt "have a clue that [Berry] was in that house, or anybody else was in there against their will."

Ramsey recalled regularly seeing Castro puttering around in the yard: "He just comes out to his backyard, plays with his dogs, tinkers with his car and motorcycles, and goes back in the house. Hes somebody where you look and then you look away, because hes not doing nothing but the average stuff."

But there seems to have been some evidence of deliberate deception on Ariel Castros part. In an interview with Londons Daily Mail newspaper, Castro's son, Anthony, said that he seldom visited his fathers house, but noted that there were locks on doors to the basement, attic and garage. When he last visited the house, two weeks ago, Anthony said his father barred him from coming inside.

• Photos of the Cleveland house investigation

Matt Logan, a forensic behavioural specialist and former RCMP officer, says theres a tendency to think that an individual would have to be fairly sophisticated in order to keep up appearances while holding another person captive for years on end.

"But the more I look at this case, Im guessing that its actually going against that," Logan told CBC News, adding that Castro was just very lucky in what he'd done.

Suggestions of abuse

On Wednesday, Cleveland police Chief Michael McGrath told NBC's morning show Today that the three young women were physically restrained and only allowed outside "very rarely" during their decade in captivity.

"We have confirmation that they were bound that there were chains and ropes in the home," McGrath said.

Wendy Christensen, a former RCMP officer who is now head of investigations for the Missing Children Society of Canada, said that keeping three women captive for so long would have to involve some sort of mental and physical intimidation.

"I find this particular case fascinating in that we have three victimsall living under the same roof for years," and that Castro was "able to keep up the facade for so long," Christensen explainedin an email interview.

"I think that this speaks to the level of terror and psychological abuse that these victims suffered on a daily if not hourly basis."

Echoes of other long-term abductions

The circumstances of the Cleveland story echo those of other long-term abductions, including that of Elizabeth Smart, a 14-year-old who was taken from her bedroom in Salt Lake City, Utah, in June 2002. She was found nine months later, being held in a house 29 kilometres from her home. Brian David Mitchell and Wanda Barzee were eventually convicted for kidnapping.

Then theres the case of Natascha Kampusch, an Austrian woman who was kidnapped by Wolfgang Priklopil in March 1998 and held in the cellar of his home outside Vienna for more than eight years. After Kampusch escaped in August 2006, Priklopil committed suicide.

• High-profile cases of children who survived abductions

Amanda Pick, executive director at the Missing Children Society of Canada, says that long-term kidnappings often lead to what is known as Stockholm syndrome, the phenomenon in which the abductee begins to identify with and even feel compassion for their abductor.

"Children begin to believe that if they co-operate, that no further harm will come to them," says Pick, adding that they "start to feel empathy and sympathy and almost positive feelings when the trauma of the abduction doesnt continue."

Victims may resist leaving

This can lead to a situation where a victim feels it is safer to stay with the abductor, former FBI profiler Brad Garrett said in a 2011 interview with CBC News.

Garrett referred to the case of Jaycee Dugard of Lake Tahoe, Calif., who was abducted in 1991 and held captive by Phillip and Nancy Garrido for 18 years. (The Garridos were sentenced to lengthy prison terms in 2011.)

"They interviewed people that said [Dugard] came to the front door of the house to talk to people [Phillip Garrido] worked with, but never stated a problem or attempted to leave. Clearly she did not feel OK leaving and felt OK on some levels to stay there," Garrett said.

• Profiling abductors: a Q&A with Brad Garrett

Christensen says that sexual abuse is often a feature of long-term abductions such as this, and that female victims may bear children while in captivity.

Police will be conducting a paternity test to determine the father of Amanda Berry's six-year-old child, who escaped with her.

One of Ariel Castros neighbours saw him out with a young child just a week ago. When he asked who the child was, Castro answered that it was the daughter of a girlfriend.

The presence of a child in a kidnapping scenario can lead to the development of a family dynamic, says Christensen, and the appearance to outsiders that the captor and captive are romantic partners.

"In those cases, people close to the abductor have been interviewed and never thought anything was wrong, as the abductee did in fact appear to be a wife or girlfriend of the abductor," says Christensen.