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Law and Crime

Idaho College Slayings: Does Motive Matter?

Why did Bryan Kohberger allegedly kill four students? Is the motive relevant?

Key points

  • Suspect Bryan Kohberger has been charged with the murders of four Idaho college students.
  • The probable cause affidavit secured for Kohberger's arrest lists the evidence that links him to the crime scene but is void of any motive.
  • The motive may be irrelevant to proving a defendant's guilt, but it enables one to make sense of psychically incomprehensible behavior.
Fer Gregory/Shutterstock
Source: Fer Gregory/Shutterstock

In the probable cause affidavit, the investigative work identifying Bryan Christopher Kohberger as the suspect allegedly responsible for murdering the four Idaho college students was made public.

Kohberger, a 28-year-old first-year Ph.D. student in criminal justice at Washington State University, was located some 10 miles from the Idaho campus and the crime scene where the slayings occurred. He finished his first semester of doctoral studies this December after completing his master’s in criminal justice in 2022 and his bachelor’s in psychology in 2020 at DeSales University in Pennsylvania.

We know little about the suspect other than he was described as a loner in high school and did not appear to have any significant intimate relationships that have been uncovered yet. Police arrested him in his parent’s home in Pennsylvania on December 30, 2022, nearly two months after Kaylee Goncalves, 21; Madison Mogen, 21; Xana Kernodle, 20; and Ethan Chapin, 20, were found fatally stabbed in an off-campus home. Multiple sources of evidence below were linked together to support Kohberger’s arrest and obtain a warrant.

1. DNA found on a button of the knife sheath in the bed next to one of the victims at the crime scene matched the suspect.

2. Trash taken from the suspect’s parent’s home in Pennsylvania was matched to DNA at the crime scene.

3. A surviving roommate described a masked figure she witnessed in the home at the time of the murders as taller than 5’10, athletic with bushy eyebrows fitting the suspect.

4. Kohberger’s phone pinged near the victims’ residence 12 times in the months before the killings. Records also show his phone was pinged near the murder scene between 9:12 a.m. and 9:21 a.m., just hours after the killings.

5. A white Hyundai Elantra was caught on surveillance circling the crime scene area multiple times before the stabbings occurred between 4–4:25 a.m. on November 13th. The car was also observed quickly leaving the address around 4:20 a.m. The vehicle was registered to Kohberger.

6. Kohberger’s phone and car were in the same locations before and after the crimes.

7. The suspect changed his car’s Pennsylvania license plate to a Washington state plate five days after the killings.

While the affidavit included all the above information connecting Kohberger to the murders, it was void of one glaring piece of evidence: a possible motive for the stabbings. The investigators may know more about why the suspect allegedly committed these heinous slayings. However, thus far, the public is being kept at bay regarding motive. The question then arises do we need to know why? Does the why matter?

Relevance of Motive

A tenet of criminal law states that a defendant’s motive for offending, be it good or bad, should have no weight in assessing their criminal liability (Eldar & Laist, 2017). This ideology is known as the “irrelevance of motive principle,” which instructs factfinders to pay sole attention to the rule of law. It is said that allowing defendants’ motives to generate or negate their culpability would undermine the state’s authority in defining a crime.

Motive is not an evidentiary element that has to be proven to find a defendant guilty of a crime. Indeed, motive can often be confused with mens rea, which requires the prosecution to establish that the alleged perpetrator intended to commit the criminal act. Conversely, motive explains why a person committed a crime, not that they did.

In the probable cause affidavit at hand, we are missing a motive by Kohberger. We do not know how the suspect knew any or all of the victims before their murders. We do not know if Kohberger knew any of these college students at all. Moreover, does the why matter here? The investigators have established mens rea with their probable cause affidavit as intent to commit a crime is outlined. It specifically delineates the evidence that ties Kohberger to the crime scene and resulting stabbings.

His DNA was found on the button of the knife sheath that was used to kill each of the four victims. His phone was pinged to the location of the slayings on multiple occasions, and his car was caught on surveillance before, during, and immediately after the murders at or near the crime scene.

So, what is it about knowing why Kohberger may have committed these heinous crimes that provide some semblance of understanding to behavior that is incomprehensible to most of us? Suppose Kohberger had some morbid fascination with criminology and serial killers, and his studies led him astray. Maybe he wanted to prove that he could get away with the perfect crime and not get caught.

What if he idolized the infamy of the serial killers he had studied for years? Does that satisfy our attempt to comprehend these horrific slaughters of four vibrant college kids? Would it make more sense to learn that the suspect had difficulty communicating with young women and felt rejected or rebuffed by one of these victims, becoming obsessed with killing her and eventually carrying this atrocity out?

The point is that the why does not matter legally. However, trying to comprehend what these victims went through on that fateful night of November 13th, in which they were viciously stabbed repeatedly, almost requires one to try and understand the why of this unthinkable horror. Indeed, the why has psychological meaning for us: “We humans have purpose on the brain. We find it difficult to look at anything without wondering what it is for, what the motive is for it, or what the purpose behind it might be” (Dawkins, 1995).

Motive plays an essential role in sense-making at various stages of the criminal justice process for the jurors and layman. We may never know why Kohberger allegedly slashed these kids to death, but somehow, the motive feels very important here to make any sense of something so acutely brutal.


Eldar, S, and Laist, E. 2017. "The Irrelevance of Motive And The Rule Of Law." New Criminal Law Review: An International and Interdisciplinary Journal, 20(3): 433-464.

Dawkins, R. (1995). God's utility function. Scientific American, 273(5), 80-85.

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