The unsolved murder case of six-year-old American child beauty queen JonBenét Ramsey in 1996 has been brought back into the media spotlight after two decades, in a special series on the Dr. Phil Show.

The victim's brother, Burke Ramsey, 29, has finally spoken about the fateful day on which his sister went missing for six hours, until she was found dead in the basement of the family home. The cause of death was strangulation and a skull fracture.

JonBenet Ramsey
Six-year-old JonBenet Ramsey was found murdered in her upscale Colorado home the morning after Christmas in 1996. Wiki Commons

To this day, many people suspect that the then nine-year-old Burke was behind the killing. So when he grinned throughout his interview with Dr. Phil as he discussed the murder, he came under fire from viewers. However, show host Dr Phil has jumped to his defence, insisting his behaviour is a result of anxiety.

One person tweeted: "Ok, #burkeRamsey is 100% creeping me out on @DrPhil his smirk is sickening. This interview is unbelievable #drphil," while another said: "Holy crap I really think Burke Ramsey killed his sister".

Dr. Phil told Entertainment Tonight: "Burke is not and has never been a suspect in this case. I think people have considered him otherwise because, in the very beginning, the DA and the Boulder PD have acknowledged and admitted they put out misinformation to the media, to the public, to try to put pressure on the Ramseys to either make a mistake or break or confess."

"Burke has been the missing link in this whole thing because in 20 years, he's never spoken. He is, as I say, the only other person known in the house," he added.

The first instalment of the three-part special for Dr. Phil aired on Monday (12 September) and some viewers were left suspicious of Burke's body language while speaking to the host. A body language specialist, Judi James, has given her insight on Burke's behaviour to IBTimes UK.

She said: "When we assess body language behaviours we compare expressions and gestures to what we consider to be 'normal'. However when we look at someone under extreme pressure, e.g. emotional trauma or appearing in court accused of a crime, there is no real 'normal' to use, as has been seen many times in court cases.

"Deep grief can make a person respond with a reflex laugh or become immobile, appearing unfeeling. Guilt can look calm and innocence can prompt displays that might be seen as 'shifty'.

"We especially forget the pressure of the kind of 'performance' someone like Burke will be under as we tend to ignore the fact that there were cameras filming his every move and a professional interviewer asking questions.

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Burke Ramsey smiles during an interview with Dr Phil Dr Phil Show

"No matter what someone's inner feelings there will always be the pressure to look normal when in reality there is no such thing. It would be easy to imagine that looking 'yourself' might involve a smile.

"Anxiety can also prompt a smile under extreme conditions. Apes use what looks like a smile gesture when they are in fact terrified and the same tightening of the lip muscles can affect humans."

"Body language is not a precise science which is why in court cases or events like this it is always important to look at facts and evidence rather than make assumptions based on the facial expressions or non-verbal behavior of anyone involved."

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Burke Ramsey speaks about his sister's murder Dr Phil Show

On that tragic day in 1996, John Ramsey and two of his friends began their search for JonBenét in the family home. After searching the bathroom and "the train room", they went into a "wine cellar" room – the basement – where John found his daughter's body covered in her special white blanket.

She had a nylon cord around her neck and her wrists were tied above her head. Her mouth was covered by duct tape. The results of the autopsy revealed that JonBenét was murdered by strangulation and a skull fracture.

At the time, Boulder law enforcement agencies initially suspected JonBenét's parents and Burke himself. But in 2008, the family were completely cleared after a DNA sample was taken from the victim's clothing. In February 2009, the Boulder Police Department took the case back from the district attorney and reopened the investigation. The case remains unsolved to this day, despite several grand jury hearings.