Like many middle-class, suburban American parents, Shannan and Joey Troiano worried about their son’s behaviour and his bad grades at high school. And like many wayward teenagers, Cory Ryder was grounded for weeks at a time, had a PlayStation confiscated and was banned from watching TV.

Less typically, this 16-year-old was plotting to murder his parents by hiring a hitman, while his mother was organising a sting operation involving a police officer posing as a contract killer.

Cory’s trial is scheduled to begin today at the circuit court in St Mary’s County, Maryland. His mother is expected to testify as a witness for the prosecution.

At an earlier court hearing Mrs Troiano, 35, explained how her emotions were torn between being an agonised mother and a murder victim. “I miss him being at home,” she said, “and I miss us joking around and kidding around. And then in the very same breath – I don’t know what this kid will do, because it’s not my son. That can’t be my little boy sitting there.”

Mrs Troiano remembers the night on June 2 when she discovered that the vague threats her son had made were serious. A woman Cory trusted, the mother of one of his friends, took him to a hotel room where he met an undercover police officer pretending to be a hitman.

At home in southern Maryland, Mrs Troiano told her husband that Cory would never go through with it and began frantically tidying the house, according to an account in The Washington Post yesterday.

After a few hours’ waiting, the policeman called: Cory was in custody and would be charged with attempted murder. Mrs Troiano fell to her knees in the bathroom she was cleaning and burst into tears.

Police say that Cory offered the undercover officer his stepfather’s new pickup truck as payment for killing his parents. “Two bullets is all it takes,” he is alleged to have said.

His mother, a financial manager at Patuxent River naval station, and stepfather, a computer specialist, had lived an ordinary life with Cory and his two stepsisters. Mrs Troiano had left his father when Cory was little more than a year old but, by the time she remarried, her son’s behaviour was getting steadily worse.

He walked out of lessons at Spring Ridge Middle School in Lexington Park, smashed a fire extinguisher case and then broke into the county fairgrounds, where he vandalised property. A judge sentenced him to supervised probation and his parents attended no less than 36 meetings with the authorities about him.

But Cory dropped out of school and then, after stealing $45 (£22) from his sister’s piggy bank, had a fight with his mother, which led to him being kicked out of home. He has since told officials that he was upset about being thrown out of the house and that he felt pressured to talk to the man in the hotel.

Cory insists that he never intended to have his parents killed and that he wanted to call the police that night in the hotel room. A judge has ruled that he should be tried in the juvenile system, which means that he cannot be held beyond his 21st birthday.

He has also been writing to his mother, saying: “You know I love you with all my heart mom!” Mrs Troiano fears that he is being manipulative. She wanted him tried in an adult court where he would have faced a much longer sentence. “He needs to understand what he did was wrong,” she told the court in September. “I’m scared to death that if this kid is serious, and they put him in a three-month programme, they’re going to release him to the street.”

Times Recommends

• Should Knox’s trial even have reached the courtroom?
• 'Was it real?' The US bailout nightmare
• Iranian opposition plays the long game