Authorities said if they could have used familial DNA technology, they likely would have found Aaron Thomas sooner.
The man accused of being the East Coast Rapist, Aaron Thomas, plead not guilty in court on Tuesday.
Thomas is being held in New Haven, Conn., where he was charged with a 2007 rape.
Two law enforcement officials say that Thomas told investigators that he committed other sexual assaults prior to the rapes he has been accused of. According to the two officials, who spoke to the Associated Press on condition of anonymity, Thomas had told investigators that he had begun raping women in 1991, at the age of 19.
The prosecutor in New Haven said that when police arrested Thomas in a Connecticut suburb early March, Thomas asked, "Why haven't you picked me up sooner?"
Thomas is believed to be responsible for rapes and other attacks on 17 women since 1997.
The most recent occurred in Virginia in 2009, where he was almost caught when a victim was able to send a text message for help to her mother. In that incident, two 17-year-olds and a 16-year-old were approached by a masked gunman in the 4300 block of Dale Boulevard on Halloween and ordered into the woods. He raped the 17-year-olds, but the 16-year-old was able to contact her mother.
Thomas faces three life sentences iIn Loudoun County.