BOULDER, Colo. -- Twenty years after JonBenet Ramsey was found dead in her parent's home on the day after Christmas, no one has been arrested but Boulder Police say the investigation continues.

Boulder's police chief said investigators have:

Processed more than 1,500 pieces of evidence

Analyzed of over 200 DNA samples

Received and reviewed or investigated more than 20,000 tips, letters or emails.

Traveled to over 18 states

Interviewed, or spoken with more than 1,000 individuals

The Colorado Bureau of Investigation will test certain pieces of evidence in the unsolved murder next year, Boulder District Attorney Stan Garnett told Denver7 earlier this month.

"DNA is a very rapidly developing area of forensic investigation, and of course, it's important for us that any of the evidence in the Ramsey case, and in any case, is tested according to the most current and updated methods," Garnett said.

"I don’t anticipate there’s going to be any dramatic developments from this round of testing, but if the rest of the case comes together at some, I want to be assured that we have state of the art DNA testing on everything in the case," Garnett told Denver7's Marc Stewart.

Garnett's office and Boulder Police investigators are working to decide which pieces should undergo the new, more sensitive testing that is now available. It's called YFiler Plus and it focuses on the Y chromosome.

The evidence likely being considered for the new testing is the duct tape found on JonBenet's mouth, the ligatures that were on her wrists, part of the garrote that strangled her and a flashlight, according to ABC News.

Garnett said while the additional DNA testing "might give us new information that could be helpful to the investigation, I don't expect that DNA test results alone will definitively solve or prove the case."

"To ever have a prosecutable case, we have to have several different pieces of evidence come together," Garnett said.

The last time any of the evidence was tested for DNA was the fall of 2008 when the wrist ligatures were sent to the CBI. The results were inconclusive.

-- Case history --

JonBenet Ramsey was found dead in the basement of her parent's home in Boulder on December 26, 1996. She was 6 years old. She died after she suffered a blow to her head, which broke her skull. She also suffered strangulation.

As we approached this anniversary of her murder, new theories have been reported.

Forensic pathologist Werner Spitz has accused JonBenet's brother, Burke, of killing his sister. Burke was nine years old when his sister died. Burke is suing Spitz for defamation.

A Lifetime Television documentary pointed the finger at JonBenet's mother, Patsy Ramsey. Patsy died in 2006 from ovarian cancer.

In October 2013, we learned that the Grand Jury that investigated the murder case in 1999 voted to indict JonBenet's parents on charges of child abuse resulting in death and accessory to a crime. However, the indictment was not accepted by then-District Attorney Alex Hunter because he said he didn't think he could prove beyond a reasonable doubt that the parents were guilty.

Read more about the case.

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