JonBenet Ramsey's brother Burke Ramsey speaks for the first time since murder

The older brother of JonBenet Ramsey oddly smiled as he recalled the moment his mum told him that his sister was missing 20 years ago.

Burke Ramsey, 29, has spoken for the first time since the murder of his sister on Boxing Day 1996.

The 1996 murder of 6-year-old beauty queen JonBenet Ramsey made international headlines and captivated the nation.

"The first thing I remember is my mom bursting in my room, really frantic, saying, 'Oh my gosh! Oh my gosh! Oh my gosh!' running around my room - now I know looking for JonBenét," Burke Ramsey told Dr Phil McGraw. "The next thing I remember is a police officer coming into my room and shining a flashlight."

JonBenet's body was eventually found tangled by a garotte with a severe blow to the head in the basement of the family's home in Boulder, Colorado.

The finger was pointed at her parents John and Patsy Ramsey and even brother, Burke.

JonBenet Ramsey performing during a beauty pageant.

It has been 20 years since the death of the child beauty pageant star but no arrests have been made.

Burke Ramsey told Dr Phil he misses his sister "very much".

Dr Phil said Burke appeared very "socially awkward" during the interview.

"People are going to be very interested in his demeanour, and they're going to find his demeanour atypical," Dr. Phil told the US Today show. "He might be talking about some pretty dark aspects of this story and smiling while he's talking about that.

John Ramsey looks on as his wife Patsy holds an advertisement promising reward for information leading to arrest and conviction of murderer of their daughter JonBenet. Photo / AP

A Dateline documentary entitled Who Killed JonBenet, set to screen in Australia on Channel Nine, features interviews with the 911 operator who took the call from Patsy Ramsey, as well as detective Jane Horner. Neither has spoken about the case publicly before.

Kimberly Archuleta who took the 911 call says it was "the hardest call I ever took."

She said even though Patsy attempted to end the call, the line was still going and she could hear "another voice."

John and Patsy Ramsey with their 10-year-old son Burke in 1997. Photo / AP

"The third voice was a male voice ... I knew there was a third distinct voice," she said.

Some suggest that third voice was Burke's.

Detective Horner said she believed a grand jury made the right call to indict John and Patsy Ramsey on charges of child abuse but that she also felt the decision not to prosecute based on the evidence was the right one.

JonBenet Ramsey performing during a beauty pageant. Photo / AP