Kidnapped boy may not have attempted escape because he was in 'survival mode'

Terri Weaver, an associate psychology professor at Saint Louis University, an expert on post traumatic stress disorder, said children in such situations kick into survival mode, "doing what needs to be done to keep yourself going day-to-day."

The case is reminiscent of the Elizabeth Smart kidnapping. The Salt Lake City teen was taken for nine months by a religious zealot and passed up several chances to escape.

Stephen Golding, a forensic psychologist who examined the suspect in the Smart case, said captors often establish control over their victims through fear.

"People are led to believe, through someone taking advantage of their vulnerabilities, that leaving is not an option, that things will get worse for them or will get worse for others," Golding said.

Shawn's kidnapper also threatened to shoot the 15-year-old after snatching him off the street.

Friends of the teenager have revealed Michael Devlin, 41, had at least three guns in the apartment where Shawn was held captive.

Tony Douglas, 15, who was Shawn's best friend, said: "We both knew there were guns in the house. Michael told us that he had the guns and were for his protection."

Shawn's stepfather Craig Akers, 45, has revealed his son's life was threatened by Devlin while he lived with him in a ground floor flat in Kirkwood, a suburb of St Louis, Missouri.

Police and psychologists will tomorrow begin to question Shawn about his four years as a prisoner. They believe he suffered "Stockholm Syndrome", where a victim begins to identify with the captor.

The teenager has yet to talk about the four years and explain why he did not try to escape. It has emerged he had ample opportunity to leave and alert the authorities.

He was stopped by police on at least three occasions while out walking after dark. Shawn also had his own mobile phone and was allowed to spend weekends at friends' houses. The teenager, who went missing when he was 11, also saw a park bench bearing a "missing" poster with his name and face on it.

Tony Douglas, who met Shawn a few weeks after he had been abducted, said they had watched a TV programme where his disappearance was discussed. When Tony pointed out that he looked like Shawn Hornbeck he said his friend shrugged and said "whatever".

He did not attend school over the last four years but but was told to say he attended a private school. He referred to Devlin as his "dad".

"Shawn has not really opened up about what happened to him, and Craig and Pam do not want to push him," said a family friend. "But they believe he became convinced that he was no longer wanted and that is why he stayed.

"As the weeks turned into months and no one came for him he began to rely on Devlin. That is the only explanation Craig and Pam believe for what has happened."