Lawyers for Idaho murder suspect Bryan Kohberger have taken testimony from a genealogist who casts doubt on the reliability of the genetic genealogy researchers used to arrest him.
Detectives relied on genetic genealogy to build their case against the 28-year-old, as they used the method to build a DNA profile from DNA left on a knife sheath at the scene – and then compared that profile to Kohberger’s father before his arrest.
While prosecutors claim they directly linked the DNA from the sheath to Kohberger after he was arrested, they first used genetic genealogy, and his defense has so far focused on examining the process used by investigators to gather evidence and build the DNA profile, arguing it was flawed or unconstitutional.
In their latest effort to retrieve the data and methods used by investigators to link the DNA evidence to Kohberger, the defense team filed an affidavit Wednesday by Dr. Leah Larkin, an expert on the subject from California.
In her affidavit, seen by DailyMail.com, Larkin argues that DNA profiles created by home testing companies such as 23andMe and AncestryDNA are not constructed in the same way as those created by specialty labs, and are not as reliable.
Lawyers for Idaho murder suspect Bryan Kohberger have taken testimony from a genealogist who casts doubt on the reliability of the genetic genealogy
The defense team has filed an affidavit from Dr. Leah Larkin, a California expert on the matter
(L-R) Housemates Dylan Mortensen, Kaylee Goncalves, Madison Mogen (on Kaylee’s shoulders) Ethan Chapin, Xana Kernodle and Bethany Funke
“A poor quality kit may have too few matches or it may just have phantom matches that are not true measures of relationship,” the document reads.
Larkin notes that sites like AncestryDNA, 23ndme, and MyHeritage prohibit forensic/investigative genealogy in their databases, but there isn’t really a way to enforce it.
“In the absence of effective oversight, forensic genetic genealogists have an ‘honor system’ to comply with the Justice Department’s Terms of Service and interim policy on forensic genetic genealogy.”
Larkin explains that the science used by these sites is not perfect, and “any given centimorgan quantity may represent more than one possible relationship.”
She notes an example with nearly 20 possible relationship lines for a match – and says that’s considered a good match.
Larkin points out that unlike DNA tests that find an individual, which are standard forensic STR tests, genetic genealogy tests identify possible relatives.
She then notes cases where she would know genetic genealogy was wrong, as well as cases where the databases were used inappropriately by authorities.
The FBI tracked down Kohberger by tracing his distant relatives through genetic genealogy databases — then secretly collected a sample of his father’s DNA to confirm his identity.
Police say DNA found on a knife left at the Idaho murder scene is a “statistical match” to a cheek swab taken from the suspect after his arrest.
A DNA sample left on the sheath is “at least 5.37 octillion times more likely to be seen if (the) defendant is the source than if an unrelated person randomly chosen from the general population is the source is,” prosecutors said in the filing.
Kohberger had no prior criminal record, meaning his DNA was not in any law enforcement database.
Genetic genealogy is an increasingly popular and useful investigative method in which law enforcement officers track down relatives of suspects on ancestral websites.
When DNA is found at the crime scene that does not belong to the victims, the first thing the police do is run it through their own database to check if it matches the DNA of previous perpetrators.
A Ka-Bar knife similar to the one believed to have been used in the murders
The former criminology student chose to “keep silent” at his arraignment last month and not guilty pleas were filed on his behalf
This process is called a short tandem repeat comparison (STR) and 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 an immediate family member’s DNA is in the system. the system (for example, a parent or sibling).
If both fail, researchers should look to genetic genealogy to look more broadly at more distant relatives.
Unlike police DNA databases, those run by commercial genealogy companies can search for up to 1 million DNA markers (using single-nucleotide polymorphisms, not STRs), creating a much wider pool of relatives to sift through.
While there are many commercial ancestry websites, only two law enforcement agencies openly allow their databases to be searched: GEDMatch and Family Tree DNA.
Once a suspect is nailed down, genealogy researchers turn over their findings to the police.
Undercover or undercover teams then track the suspect and surreptitiously obtain a sample from them to compare to the sample found at the crime scene used in the DNA search.
Kohberger is accused of stabbing to death student Ethan Chapin, 20; Madison May, 21; Xana Kernodle, 20, and Kaylee Goncalves, 21, in Moscow, Idaho, on Nov. 13, 2022.
Detectives found a Ka-Bar knife sheath on the bed containing the bodies of Mogen and Goncalves. The scabbard was partially under Mogen’s body and the comforter on the bed, according to court documents filed June 16.
Investigators later closely matched the DNA on the sheath with DNA found in trash taken from Kohberger’s parents’ home in Pennsylvania, where he was arrested in December 2022.
The students’ bodies were found in a rental home across the street from the University of Idaho campus.
The murders shocked the rural community of Idaho and neighboring Pullman, Washington, where Kohberger was a graduate student studying criminology at Washington State University.
Kohberger is being held in the Latah County Jail in Moscow, Idaho, on charges of first degree murder and burglary. His trial begins on October 2.
He has pleaded not guilty and faces the death penalty.