SEATTLE — Since the arrest of suspected Idaho murderer Bryan Kohberger's arrest nearly two weeks ago, authorities have released several key details of how police linked him to the crime, including the use of DNA.
Court documents revealed the DNA from a lone male was found on a knife sheath recovered from the home where the victims were killed matched DNA from Kohberger's father taken from the trash outside their family home in Pennsylvania.
According to Cairenn Binder with the DNA Doe Project, that type of match comes from STR DNA or short tandem repeat analysis.
"When you abandon your DNA, or your direct family member abandons their DNA at a restaurant...on the ground or things like that, that can be collected by law enforcement," said Binder who is the Director of Education and Training for the DNA Doe Project.
The DNA Doe Project is an organization known for its work with DNA on several high-profile cases, including working with the King County Sheriff's Office to identify the last four victims of the Green River killer.
Binder said DNA from STR analysis is the only evidence currently admissible in court and the only DNA testing that shows a one-to-one match or a match to a direct relative.
Genetic Genealogy uses what is called SNP sequencing and can match a sample found at a crime scene much further back to a fifth or sixth cousin, for example.
Binder explained it as a high-resolution photo versus a low-resolution photo.
"That wouldn't necessarily be the thing that leads to the arrest because what they really want is the STR test, the one-to-one STR test of the suspect DNA," Binder said.
SNP sequencing is newer technology most famous for being used to catch the Golden State Killer, but there has been no confirmation from authorities on if or how it was used to initially link the murders in Idaho to Kohberger.
Binder said it's possible it was used in this case as SNP sequencing is being used more and more to identify suspects that don't come up in CODIS - the national database comprised of several indexes including DNA profiles from convicted offenders.
However, STR analysis is the standard and that is what police made public along with the other pieces of evidence including the phone records and the white Hyundai Elantra.
"It's really important for law enforcement to do their traditional investigation, cellphone records, eyewitnesses, fingerprints, all of the things that we've had for a long time because DNA is only one piece of the puzzle and you've got to have the whole case together," said Binder who adds that now it's up to the defense to investigate how the DNA was collected, if it was legal, and followed procedure.