The Denver District Attorney's Office said a defendant in multiple sex assaults, William Costello, killed himself Thursday morning.
Costello's trial in a series of sex assaults dating back to 2008 started this week in Denver District Court.
The court declared a mistrial Thursday morning after learning that Costello took his own life.
According to police, he did not show up for his 8:30 a.m. trial. The court waited, but after a while decided to monitor him using GPS.
The GPS had him at various locations, but he was later found in the area of Brighton Boulevard by paramedics.
"It's sad resolution, but it is a resolution. There are a lot of people that have waited a lot of years for Mr. Costello to be held accountable for what he did," Denver District Attorney Mitch Morrissey said.
"He wasn't a good guy, he lived a double life. He's out raping women in our community, while he's putting on this front [as a] good dad ...Realtor, those types of things. That's why DNA is so important, because it uncovers people like this," Morrissey said.
9NEWS reached Elizabeth, a 19-year-old who was 13 when court documents say Costello raped her felt like justice won't be done.
"I think it's sad," she said. "I think he did it because he didn't want to face the consequences of what would happen to him."
Police did not release his cause of death yet. ..Source.. by Tim Ryan, KUSA
DNA evidence links man to unsolved assaults
What started as an arrest for an assault turned into a trial on three sex assault cold cases in Denver.
The Denver District Attorney's Office says Katie's Law allowed the detectives to take William Costello's DNA after the alleged assault, which is a felony.
The Colorado Legislature enacted Katie's Law, which allows every adult arrested or being investigated for a felony on or after Sept. 30, 2010 will submit to a DNA sample as part of the booking process.
Investigators say Costello's DNA has been linked to three unsolved sex-assault cases in 2008, 2010 and 2011.
The 49-year-old is on trial this week in Denver on 18 counts, including multiple counts of sex assault on a child, sex assault and kidnapping.
The trial is expected to last a week, with all three sex-assault victims testifying.
Costello's first alleged victim was 13 at the time of the sexual assault in 2008. She is now 19 years old.
She told detectives Costello picked her up on the street after she ran away from Denver Children's Home.
"I was just walking down the street, and I happen to run into him and asked him for directions," the victim "Elizabeth" said. "He told me to get into his car and he'd give me a ride. I got into the car because he had a one-and-a-half-year-old son in the back seat. I kind of figured he was harmless."
According to the arrest affidavit, Costello wasn't.
Back then, Elizabeth just knew him as Will.
"After he raped me twice, he let me go with the promise to not tell nobody," Elizabeth said.
She told police, they did a rape kit. But even with the suspect's DNA and Elizabeth's description, six years went by with no arrests.
"I lost hope," she said.
Costello was busted for an aggravated assault 2012; a felony.
According to the arrest affidavit in that case, Costello assaulted an older man collecting petition signatures outside a grocery store. Court documents say Costello pushed the man off his bike, which caused a broken hip.
After the alleged assault, Costello's DNA was taken and it matched three cold sex assault cases, including Elizabeth's. In two of those cases, records show Costello told his victims he was a police officer.
This trial is expected to last a week, with two other sex assault victims testifying.
Costello has also been charged in a fourth sex assault case unrelated to the cold cases. That trial is expected later this month, as well as the trial on the assault case.
Neither Costello nor his attorneys had comment Wednesday.
Costello is out on bond. ..Source.. by Anastasiya Bolton, KUSA