MOSCOW, ID – Prosecutors in the case against Bryan Kohberger, the man accused of killing four University of Idaho students, maintain that a DNA match from a knife sheath remains a key piece of evidence, according to newly filed court documents.
The state’s response to a defense motion, filed this week, reaffirms that investigative genetic genealogy was used only as an initial lead-generating tool and did not contribute to the confirmatory DNA match linking Kohberger to the scene. Prosecutors argue that the short tandem repeat (STR) DNA comparison—not investigative genetic genealogy—established that DNA found on the knife sheath matched Kohberger’s profile.
The court filing also states that Kohberger’s own forensic expert has not challenged the DNA match. Instead, the defense appears to be shifting its argument, suggesting that while the DNA on the knife sheath belongs to Kohberger, the item could have been planted at the scene by another party.
The defense had filed a motion to exclude investigative genetic genealogy-related evidence, arguing that the prosecution mishandled discovery and withheld key information about lab protocols. However, the prosecution counters that the process was never intended to be used at trial and only served as a tip for investigators.
While the state acknowledges an oversight in disclosing certain lab procedures from the private lab Othram, prosecutors argue that this information is immaterial to the case, given that the final DNA match was based on a separate confirmatory STR comparison.
In a rare point of agreement, both sides now support excluding investigative genetic genealogy evidence from trial, with the prosecution stating that its only use would have been to explain investigative steps to the jury. The state asserts that it will refer to the process as a generic tip rather than disclosing its details.
Kohberger is accused of fatally stabbing Madison Mogen, Kaylee Goncalves, Xana Kernodle, and Ethan Chapin at an off-campus home in Moscow in November 2022.
With the trial approaching, the focus remains on the knife sheath as a pivotal piece of forensic evidence linking Kohberger to the crime scene. The trial is set to begin in August.
