Attorneys for Idaho murder suspect Bryan Kohberger have produced a genealogist’s testimony that casts doubt on the reliability of the genetic genealogy investigators used in his arrest.
Investigators used genetic genealogy to base their charge against the 28-year-old, using that method to create a DNA profile from DNA left on a knife sheath at the scene — and then matching that profile to Kohberger’s father before his arrest.
While prosecutors claim they matched the DNA from the case directly to Kohberger after his arrest, they initially used genetic genealogy, and his defense has so far focused on examining the evidence-gathering and DNA-profiling process used by investigators and argues that it could have been flawed or unconstitutional.
In its latest attempt to request the data and methods used by investigators to match the DNA evidence to Kohberger, the defense team Wednesday submitted an affidavit from Dr. Leah Larkin, an expert in the field from California.
In her affidavit seen by , Larkin argues that DNA profiles created by home testing companies like 23andMe and AncestryDNA weren’t created in the same way as those by specialized labs and aren’t as reliable.
Attorneys for Idaho murder suspect Bryan Kohberger have produced testimony from a genealogist that casts doubt on the reliability of the genetic genealogy
The defense team received an affidavit from Dr. Leah Larkin, an expert in the field from California
(LR) Roommates Dylan Mortensen, Kaylee Goncalves, Madison Mogen (on Kaylee’s shoulders), Ethan Chapin, Xana Kernodle and Bethany Funke
“A poor-quality jersey may have too few matches, or it may only contain phantom matches that do not represent true measures of the relationship,” the document reads.
Larkin points out that sites like AncestryDNA, 23ndme, and MyHeritage prohibit forensic/investigative genetic genealogy in their databases, but there’s no real way to enforce it.
“In the absence of effective oversight, forensic genetic genealogists are subject to a ‘honor system’ to comply with the Terms of Service and the Department of Justice interim policy on forensic genetic genealogy.”
Larkin states that the science used by these websites is imperfect and “any given centimorgan set may represent more than one possible relationship”.
She notes an example that lists almost 20 possible relationship lines for a match – and says that counts as a close match.
Larkin points out that unlike DNA tests, which find an individual and are standard forensic STR tests, genetic genealogy tests identify possible relatives.
She then notes instances of which she allegedly was aware where the genetic genealogy was incorrect, as well as instances where the databases were misused by the authorities.
The FBI located Kohberger by tracing his distant relatives using genetic genealogy databases — and then secretly collected a DNA sample from his father to confirm his identity.
Police say the DNA found on a knife sheath left at the Idaho crime scene is a “statistical match” with a cheek swab taken from the suspect after his arrest.
The likelihood of seeing a sample of DNA left on the case is “at least 5.37 octillion times more likely when the source is the suspect than when the source is an unrelated person chosen at random from the general population.” , prosecutors said in the filing.
Kohberger had no criminal record, meaning his DNA was not in any law enforcement database.
Genetic genealogy is an increasingly popular and useful investigative method that law enforcement uses to track suspects’ relatives through ancestry websites.
If DNA is found at a crime scene that does not belong to the victims, police first search their own database to see if it matches DNA from previous offenders.
A Ka-Bar knife similar to the one believed to have been used in the murders
The former criminology student decided last month to remain “silent” on his charges and pleas of innocence have been filed on his behalf
This process is called an STR (short tandem repeat) comparison, and it tests the sample against 20 DNA markers—enough to identify the person if their own DNA is already in the system, or in some cases if the DNA an immediate person is a relative in the system (e.g. a parent or sibling).
If both are true, investigators must turn to genetic genealogy to conduct a more comprehensive search for more distant relatives.
Unlike law enforcement DNA databases, commercial genealogy company databases can search up to one million DNA markers (using single nucleotide polymorphisms, not STRs), creating a much larger pool of relatives to search.
Although there are many commercial ancestry websites, only two allow law enforcement to openly search their databases: GEDMatch and Family Tree DNA.
Once a suspect is pinned down, genealogical investigators turn their findings over to the police.
Undercover or undercover teams then track the suspect and secretly obtain a sample from him to compare with the sample found at the crime scene, which was used for DNA tracing.
Kohberger is accused of stabbing students. Ethan Chapin, 20; Madison Mogen, 21; Xana Kernodle, 20, and Kaylee Goncalves, 21, in Moscow, Idaho on November 13, 2022.
Investigators found a Ka-Bar knife sheath on the bed containing the bodies of Mogen and Goncalves. According to court documents filed on June 16, the casing was partially underneath Mogen’s body and the duvet on the bed.
Investigators later closely compared the DNA on the case to DNA found in trash taken from Kohberger’s childhood home in Pennsylvania, where he was arrested in December 2022.
The bodies of the students were found in a rental building across from the University of Idaho campus.
The killings shocked the rural community in Idaho and in neighboring Pullman, Washington, where Kohberger was a graduate student in criminology at Washington State University.
Kohberger is being held on first-degree murder and burglary charges at the Latah County Jail in Moscow, Idaho. His trial is scheduled to begin on October 2nd.
He has pleaded not guilty and faces the death penalty.