Chris Watts murdered his pregnant wife and their two children in 2018, a story which has become the focus of new Netflix documentary American Murder: The Family Next Door.
The harrowing film uses police tapes, social media posts, and bodycam footage to tell the story of the tragic deaths of Shanann, 34, and her two children, Bella, four, and Celeste, three.
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But while Chris tried to hide the truth from police, his actions throughout the investigation led officers to suspect that something was up.
In a previous documentary about the murders - Capturing Chris Watts - body language experts and detectives explain exactly what gave the father-of-two away.
During initial footage from an officer's bodycam, taken at the couple's house just after Shanann was reported missing, Chris can be seen running to meet the cop.
And while Chris lets the officer into his house, he doesn't appear to be very worried or helpful with the search for his wife.
Body language expert Susan Constantine says: "It means that he is separating himself from what is being spoken at that time.
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"He's wanting to deflect. So, anytime he wants to walk away, he'll turn his back or he'll busy himself with the cell phone."
As he leads the officer through his house, Chris starts talking about his wife's migraines and how they had increased recently, all of which gave rise to suspicion.
Homicide prosecutor Jarrett Ferentino explained: "These are things that he just seems to be filling the air with some biographical information, but he's still not panicking.
"His daughters are missing and Shanann is missing and he's just providing with some, in my opinion, useless information that goes nowhere."
Then things get worse as Chris and the attending officer go over to a neighbour's house to check his CCTV footage from the night before.
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Knowing he is in the footage, Chris paces around with his hands on his head, constantly checking his phone.
Constantine says: "He's afraid to look at it because of what it might reveal, so part of it is that deflection, right? So, 'What I don't know, maybe I don't need to know'."
As the footage rolls on, Constantine says she noticed a 'cluster' of body language - curled lips, hands clasped behind his head - which all pointed towards deception.
When this was added with the failure of his marriage, his affair with co-worker Nichol Kessinger, and his plans to leave Shanann, which Chris admitted during questioning, detectives' suspicions were raised even further.
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In court, Watts admitted his guilt as part of a plea deal to avoid the death penalty and was sentenced to life in prison without the possibility of parole in November 2018.
American Murder: The Family Next Door is available to watch on Netflix now.
Topics: Entertainment, True Crime, US News, crime, US Entertainment