Since JonBenet Ramsey was found dead on Dec. 26, 1996, multiple theories have swirled around the world as to who killed the 6-year-old beauty queen.

Twenty years later, there is no definitive answer.

There are, however, two schools of thought:

1. That the crime was committed by a family member

2. An intruder broke into the Ramsey home and wrote the bizarre ransom note

Here are some of the people who have been floated as possible suspects:

John and Patsy Ramsey

In this 12 October, 2000, file photo John (R) and Patsy Ramsey answer questions from journalism students about their experience in the media spotlight at the Newseum in Rosslyn, Virginia.

One theory is that Patsy Ramsey accidentally killed JonBenet in a fit of rage after a bed-wetting incident. Proponents of this theory says she staged the crime scene and the ransom note.

Others have claimed that John Ramsey abused and killed JonBenet – something that the family has fiercely disputed.

John and Patsy Ramsey were indicted by a Boulder County grand jury for child abuse resulting in death, but the district attorney at the time declined to file charges, saying there was insufficient evidence.

Patsy and John Ramsey was cleared by touch DNA evidence in 2008. They also received an apology from the Boulder DA's office.

Burke Ramsey

A 2006 photo of John Ramsey hugging son Burke at the graves of Patsy and JonBenet Ramsey. 

In a CBS special that aired earlier this year, a forensic pathologist alleged that then-9-year-old Burke Ramsey killed his sister in a fit of rage over a bowl of pineapple, and his parents covered it up.

Burke has made good on a threat to sue for defamation, and wants $150 million in damages from the pathologist.

Like his parents, he was cleared by touch DNA evidence in 2008.

John Mark Karr

Bangkok, THAILAND: Unidentified US officials escort US teacher John Mark Karr (C) at the Thai Immigration Department in Bangkok, 17 August 2006.

Investigators thought they had a break in the case when elementary school teacher John Mark Karr confessed to the killing in 2006.

However, this confession proved to be false, and there is no DNA evidence that ties Karr to the murder. In fact, he may not have been anywhere near Boulder at the time.

Gary Oliva

Gary Oliva, 52, appears in court Tuesday at the Boulder County Jail, where he was charged with sexual exploitation of a child. 

Lou Smit, a Colorado Springs homicide detective who was hired to help with the JonBenet Ramsey investigation, was among the staunchest supporters of the intruder theory.

He brought up Gary Oliva as a possible suspect, saying the registered sex offender and known pedophile was near the Ramsey house the night she was killed.

The Daily Camera reports that Smit also alleged Oliva was at a candlelight vigil at the house the year after the crime.

A CBS program says that Oliva called a close friend after the murder and said he had “done something horrible.”

When he was arrested in 2000, a photograph of JonBenet was found among his personal property, as well as a poem called “Ode to JonBenet.”

He denied committing the crime in an interview with CBS, and was arrested this year on child porn charges.

Michael Helgoth

BOULDER, CO - AUGUST 17: A single red rose lays near the entrance to the residence at 749 15th Street, where JonBenet Ramsey was murdered in December, 1996, 

Helgoth worked near the Ramsey family home, and had a history of violence and sexual abuse. He also allegedly told a friend that he and a business partner would be making $50,000 to $80,000 around the time of the murder – roughly the amount asked for in the ransom note.

The District Attorney announced they had narrowed down a list of suspects in January 1997. Two days later, Helgoth was found dead with an apparently self-inflicted gunshot wound.

“Santa Claus”

Christmas decorations in front of the Ramsey home. 

Some theorize that a family friend named Bill McReynolds, who saw JonBenet the night before the murder, was responsible. He was dressed as Santa Claus, and was believed to have taken a special liking to the girl.

He was never formally charged, and no evidence links him to the crime.