The chilling Google searches of Chris Watts' mistress before and after he murdered his family.

The search history on the phone belonging to Chris Watts’ mistress paints a chilling picture of what she expected her life to be before and after he murdered his family.

Nichol Kessinger was having an affair with Watts before he killed his pregnant wife Shannan, and daughters Bella, four, and Celeste, three, and disposed of their bodies at his oil refinery workplace.

According to the newly-released search history investigators found on her phone, Kessinger was hopeful her Colorado boyfriend was about to leave his wife, googling wedding dresses.

People reports the 30-year-old, who was Watts’ colleague, spent more than two hours searching for wedding dresses one week before Watts murdered his wife and daughters.

But days after the murders in the early hours of August 13, when Kessinger suspected what her boyfriend had done, she was quick to investigate how she could come out of the situation well.

She googled how much money Amber Frey made in her book deal, as well as her net worth and "did people hate Amber Frey".

Amber Frey was dating California man Scott Peterson when he murdered his wife Laci and their unborn son Connor in December 2002. Frey had only met Scott less than two months earlier, and maintains that she did not know he was married.

She wrote a book about her experience of helping the police to prosecute her boyfriend, Witness. The book became a New York Times best-seller.

Kessinger claims she was in a very similar position.

In an interview with the Denver Post, Kessinger said that on the afternoon of August 13 Watts had kept up his public lie they hadn't returned from a playdate, telling her in a text that his family was "gone".

The 30-year-old said he never wore his wedding ring and she only learned he was very much still married - and not in the process of a divorce like he had told her - when she read the news about his family's disappearance.

"I thought, "If he was able to lie to me and hide something that big, what else was he lying about?'" she said.

And that's when she approached police to help.

However, the Google searches found in her history seem to suggest Kessinger was far more aware of Watts' wife and children than she let on.

Almost a month into their relationship, on July 24, Kessinger googled the phrase "Man I’m having affair with says he will leave his wife".

Then less than a week before the murders she searched topics relating to "marrying your mistress".

On August 15, police arrested Watts, who initially denied killing his family before making a confession after the six-hour long police interview.

By pleading guilty to the murders in court earlier this month, Watts avoided a death sentence and instead was sentenced on 19 November to life in jail without parole.