JonBenét Ramsey's Killer Was 'Sexually Sadistic,' Detective Says in New Dateline Special

This year marks the 20th anniversary of the murder of six-year-old JonBenét Ramsey, who was found dead in the basement of her family’s home in Boulder, Colorado, on Dec. 26, 1996.

Many theories – but few answers – have been found in the wake of the child beauty pageant's death, despite years of investigation.

On Friday, NBC Dateline will air a two-hour special, Who Killed JonBenét?, on the JonBenét, who was found strangled by a garrote with a severe blow to the head. The show will feature exclusive interviews with former detectives involved in the investigation and the 911 operator who took the call of Patsy Ramsey, JonBenét's mother, that fateful morning.

The Ramsey family has long maintained that an intruder broke into their home and killed their daughter.

In the special, former Boulder police department detective Jane Harmer discusses why she was supportive of the grand jury's decision to indict JonBenét's parents – but also why she also felt that the district attorney’s choice not to pursue charges against the Ramseys was the right one.

• Want to keep up with the latest crime coverage? Click here to get breaking crime news, ongoing trial coverage and details of intriguing unsolved cases in the True Crime Newsletter.

Also featured in the special are interviews with Tom Haney, a former Denver detective brought in by Boulder authorities to interview Patsy Ramsey, and retired Boulder detective Bob Whitson, who was at the Ramsey's Tudor home on the day the murder investigation was launched and became an advocate of the "Intruder Theory."

"The behavior at the scene does not match up" with the Ramseys, Whitson tells Dateline. "It matches up a sexually sadistic person and a psychopath."

The show will also highlight tapes of the police interview with JonBenet's brother Burke as well as an interview with Pam Barday, a Ramsey family friend.

“Who Killed JonBenét?” premieres on Sept. 9 (9 p.m. ET/PT) on NBC.