A homeless street preacher who kidnapped a 14-year-old girl in the US state of Utah in 2002 has been ordered to spend life in prison.

Elizabeth Smart, who was held captive for nine months by Brian David Mitchell, looked on as he was sentenced in a federal court in Salt Lake City.

"I know that you know what you did is wrong," Ms Smart told Mitchell.

Mitchell was found guilty in December of abduction and the transportation of a minor across state lines for sex.

The 57-year-old preacher, who had pleaded insanity in December, was handed two life sentences by US District Judge Dale Kimball in federal court in Salt Lake City on Wednesday, years after he was declared mentally ill and unfit to stand trial in state court....