According to the Washington Post, Helen and James Briggs adopted the boy six years ago, after Mrs Briggs - a foster mother - fell in love with him.

But in 2003 the boy, who cannot be named, sexually abused a six-year-old boy and a two-year-old girl.

Mrs Briggs said it was only then that she discovered his troubled past.

The newspaper said confidential files revealed that the boy's biological parents, who were alcohol and drug addicts, had physically abused him to the extent that his brain stem was damaged - hindering his ability to gauge the passage of time.

The files also suggested that he had been sexually abused.

The boy had been in and out of five foster homes since he was 16 months old, in psychiatric institutions seven times and diagnosed as possibly psychotically bipolar.

'Wrongful adoption'

Mrs Briggs said she had not been told any of those details before she adopted him. "They just told me he was hyperactive," she told the Washington Post.

Under Virginia policy, caseworkers must provide the full facts about a child to adoptive parents.

She never would have adopted the boy and put other children in danger if she had had the information that was withheld from her

David Albo

Virginia politician

State child welfare officials have not commented on the case, due to confidentiality.

But the newspaper claims some caseworkers do not believe that Mrs Briggs was uninformed.

A Fairfax County court has allowed Mrs Briggs to relinquish custody of the boy, but she is still bound to pay $427 a month in child support and cover the court costs when a judge makes a decision on his future.

Mrs Briggs, 57, could have filed a "wrongful adoption" lawsuit within two years of discovering the boy's true history, but failed to.

'Sexual predator'

She had wanted to bring the boy home after his sex offender treatment, following the case in 2003.

But then psychologists labelled him a sexual predator, meaning she would have to give up being a foster parent, which she sees as her livelihood, and would no longer be able to allow her three grandchildren in the house or keep a young girl she had fostered from birth.

Mrs Briggs decided to dissolve the adoption, which requires the consent of the boy, who is now back in foster care. But so far he has refused.

She is said to be asking politicians to help her find a way out.

"At first blush, you think 'What, you're trying to give up your kid?'", Virginia politician David Albo told the Washington Post.

"Then you find out this lady has received awards for all the foster work she's done. And that she never would have adopted the boy and put other children in danger if she had had the information that was withheld from her."