A 53-year-old Westminster man pleaded guilty to first-degree assault and obstruction of justice yesterday for attacking a female hitchhiker nearly 20 years ago and then trying to intimidate her so that she would not testify against him.

Before dawn in November 1988, a 23-year-old woman hitched a ride with a man in Brooklyn Park, but once she got into his car, she saw that he was nearly naked and had a knife, according to court documents.

The man ordered the woman to strip, then forced her to perform sexual acts with him in the woods before letting her go, according to the documents.

Almost exactly 18 years later, in November 2006, DNA from the attacker was linked to Walter G. Mitchell, 53, a Westminster man who had been convicted of arson for burning down the house of his girlfriend's sister in Carroll County after the two women had argued, according to documents. He had been sentenced to 25 years with 10 years suspended in that case.

In May 2007, Mitchell was indicted and charged with a sex offense in the 1988 attack. According to court documents, a jail informant told police that Mitchell had announced he wanted to hire someone to intimidate the woman who would testify against him in the sex offense case.

In August, Mitchell offered an undercover officer $500 and asked him to do something to the woman's house or vehicle "to give her the message not to show up for court," according to the documents.

According to the plea deal agreed upon by Assistant State's Attorney Kathleen E. Rogers and defense attorneys Karl H. Gordon and Gary Proctor and announced in Anne Arundel Circuit Judge Michele D. Jaklitsch's courtroom, Mitchell will be sentenced to 17 years for the assault and a concurrent five-year sentence for obstruction of justice.