The man accused of being the East Coast Rapist will present an insanity defense at his upcoming trial in Prince William County.

Defense attorney Ronald Fahy wrote in a court filing last week that 40-year-old Aaron H. Thomas "will put in issue his sanity at the time of the crime charged" and might call a mental health expert to testify.

Thomas was apprehended last year in his hometown of New Haven, Conn., and is suspected in up to 17 assaults along the East Coast between 1997 and 2009. He is first facing trial in Prince William for allegedly attacking three teenage girls in Dale City on Halloween night 2009.

Thomas has "complained of an alternate personality named Erwin, active at the time of the alleged offenses and suggestive of possible dissociative identity disorder," defense attorneys wrote in court documents.

A Prince William grand jury indicted him in April on eight charges: two counts of rape, three counts of abduction with intent to defile and three counts of using a firearm during a felony. Authorities say he raped two 17-year-old girls at gunpoint; a third victim, a 16-year-old girl, sent a text message for help from her cellphone.

His attorneys also say Thomas is incompetent to stand trial because he cannot understand the proceedings against him.

Thomas has "continued to mutilate his body" and will not meet with his attorneys, Jennifer Zary, another defense lawyer, wrote in a motion requesting a competency evaluation. When an attorney went to his cell, Zary wrote, Thomas hid under a blanket until she left.

Thomas has also experienced auditory and visual hallucinations, according to his lawyers.

But prosecutors say an initial evaluation found Thomas competent and determined he was only pretending to have mental health issues.

A report by the doctor who evaluated Thomas said he was "feigning or greatly exaggerating any mental symptoms he may be experiencing in order to avoid prosecution by being deemed incompetent," according to a prosecution motion filed Friday.

Thomas' two-day trial is slated to begin July 31, and a hearing in the case is scheduled for Friday.