More DNA links suspect Bryan Kohberger to University of Idaho murders: FBI

PHILADELPHIA (WPVI) -- The DNA of Bryan Kohberger, the suspect in the stabbing deaths of four University of Idaho students at an off-campus home in Moscow last fall, is a "statistical match" to DNA collected from the sheath of a knife found at the scene, according to court documents filed by prosecutors.

An "STR" analysis - or short tandem repeat analysis - is a common type of DNA profiling in criminal cases and other types of forensic cases, according to the National Institute of Justice.

"The STR profile is at least 5.37 octillion times more likely to be seen if (the) Defendant is the source than if an unrelated individual randomly selected from the general population is the source," prosecutors said in the filing. An octillion is a number equal to a 1 followed by 27 zeros.

The FBI originally loaded the DNA profile from the knife sheath onto publicly available genealogy sites, the documents state. The knife still has not been found.

That tip "pointed law enforcement toward (the) Defendant, but it did not provide law enforcement with substantive evidence of guilt," according to the prosecutors' filing - which is why they followed up using an STR analysis.

A DNA sample from trash recovered from the Kohberger family residence in the Poconos by Pennsylvania law enforcement and sent to the Idaho State Lab for testing was also used to help investigators hone in on Kohberger as a suspect in the killings, court documents released earlier this year state.

"There have been countless convictions or murder cases, both here and around the country where the murder weapon was never recovered," said Fortunato Perri, Jr., a defense attorney in Philadelphia.

While Perri is not involved in this case, he's looking to see how the defense responds to the evidence.

"You'll have to get a DNA expert onboard who could challenge the findings that the prosecution has at this point," said Perri.

The tracking of Kohberger's phone was also key to the investigation to help police pinpoint his location near the victims' home the night of the murders.

"The evidence at this point appears to be overwhelming against the defendant and they ought to be at some point sitting down trying to resolve this case with some type of a guilty plea resolution," said Perri.

Kohberger faces four counts of first-degree murder and one count of burglary in the November 13 killings of Kaylee Goncalves, 21; Madison Mogen, 21; Xana Kernodle, 20; and Ethan Chapin, 20, at a home just outside the university's main campus in Moscow.

A not guilty plea was entered on his behalf by an Idaho judge at a hearing last month.

Kohberger faces life in prison if convicted.

The trial is still set for October.

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