Watts, who was charged in August with his pregnant wife and daughters' deaths, will face three consecutive life sentences for the murder charges; the rest will be "left to the discretion of the court" when Watts is officially sentenced on November 19, the Weld district attorney previously said.
Watts told police he'd been having an affair with a coworker and revealed to his wife that he wanted to "go through with a separation", according to an arrest affidavit obtained by Oxygen.com back in August.
Kessinger sat down for an exclusive interview with the Denver Post, telling the newspaper, "He's a liar".
As she grew more and more suspicious, Kessinger reached out to the Weld County Sheriff's Office to tell them about their relationship and the lies, the Post reported.
A Colorado woman who was dating Christopher Watts - the man accused of killing his pregnant wife and daughters in August - reportedly labeled him "a liar" during an interview Thursday where she detailed how the two met and began what, unknowingly to her, was an extramarital affair.
"I believed him", she told the newspaper.
Nichol Kessinger told the Post she started dating Watts in July.
"He made me believe that he was doing all of the things that a rational man and good father would do", she said.
Kessinger only found out from news reports later that day that he was still married to his 34-year-old wife and that she was 15 weeks pregnant at the time of her murder.
"When I read the news, I found out he was still married and his wife was 15 weeks pregnant", Kessinger said.
Kessinger told the paper she peppered her boyfriend with questions but said he would try to change the subject.
Kessinger told the Denver Post that she believes that her former over killed his family.
They started seeing each other four or five times a week, but Kessinger said she insisted they take it slow as his daughters adjusted to the split. "He lied about everything". Shan'ann had taken their daughters on a playdate and they hadn't returned, she said her told her. "I was very confused why the media was at his house", she admitted.
Kessinger said that something seemed "off" about his story.
The girls' bodies were found submerged in an oil tank, and Shanann Watts' body was found in a shallow grave. Upon her return, the couple reportedly held an emotional conversation about the status of their marriage.