Devon Erickson 6.10.21

Devon Erickson, far left, watches an expert witness in physiology testify in his defense on June 6, 2021. Erickson is accused of dozens of charges, including first-degree murder and attempted murder, in connection with the May 2019 shooting attack at STEM School Highlands Ranch.

When three of Devon Erickson’s classmates tackled him after he pulled out a gun in Room 107 and shouted “Nobody [expletive] move,” they likely elicited reflexive reactions that could have led him to unintentionally fire four shots, an expert for his defense testified.

Erickson, 20, is accused of killing classmate Kendrick Castillo and wounding two others in the May 2019 mass shooting at STEM School Highlands Ranch that injured eight people. But his defense attorneys have argued Erickson’s co-defendant, Alec McKinney, coerced Erickson into participating and that he did not intend to shoot.

Erickson faces dozens of charges, including first-degree murder and attempted murder.

Prosecutors wrapped up their case Thursday afternoon. Erickson’s defense attorneys began their case shortly afterward by calling Dr. Roger Enoka, a physiology professor at the University of Colorado Boulder. The court admitted him as an expert in physiology and involuntary muscle contractions related to unintentional discharge of firearms. 

Enoka testified about theories he previously developed about how involuntary reflexes could lead to a person accidentally firing a gun they are holding. In his opinion, he said, when students rushed at Erickson after he pulled out a gun, it likely elicited a startled response and definitely caused him to lose his balance. Each may have led to Erickson unintentionally firing, Enoka said.

“Basically a startled reaction is a defensive reaction,” Enoka said. “It turns out that when you elicit these startled reactions, the first thing that happens is your eyes will blink, and very soon after that, you will squeeze the hands to make a fist. … So if you happen to be holding a gun [during] this startled reaction, it’s very easy — well, it’s plausible — that the squeezing of the gun could cause it to discharge.”

Enoka said he formed his opinion after reviewing testimony given by others who were in Room 107 at the time of the shooting. The speed with which Brendan Bialy, Castillo and Joshua Jones reacted to rush at Erickson when he pulled out a gun, Enoka said, likely factored into a startled reflex.

“It was immediate, was my impression from the statements,” Enoka said. “So if a person was not expecting such a response, it could easily be a startled reflex.”

When a person is about to fall, he added, their reflexes will try to protect whatever they have in their hands by gripping them more firmly.

Prosecutor Christopher Gallo used his cross-examination of Enoka to focus on a lack of certainty, or even probability, that Erickson’s firing of his gun was unintentional.

“Your testimony is not that this was most definitely an unintentional discharge of a gun, is that correct?” Gallo asked.

“That is correct,” Enoka said.

“Your testimony is not even that this was probably an unintentional discharge of a gun, am I correct in that, Doctor?” Gallo continued.

“Well, I don’t have any evidence to indicate a level of probability,” Enoka said.

“Your testimony, if I understand, Doctor, is that circumstances exist that an unintentional discharge of a gun could have happened. Is that fair?” Gallo asked.

“That is fair, yeah,” Enoka replied.

Gallo also highlighted Enoka’s lack of expertise about the psychology of a person holding a weapon, pointing out that one factor in a situation Enoka said could contribute to eliciting a startled response, unexpectedness, involves an assumption on his part about the person’s state of mind.

“Is there any principle known to you, studying this field, that an assailant – that a person that is not pulling a weapon in defense of themselves – should not expect potential victims to rise up in defense of themselves?” Gallo asked.

“I am a physiologist. I cannot answer that kind of a question,” Enoka replied.

“If you cannot answer that question, sir, the idea that this was unexpected is slightly outside of your expertise, is it not?” Gallo said.

He wrapped up his cross-examination by pointing out that Erickson’s actions before firing, including loading the gun, concealing it and pulling it out, couldn’t be considered an involuntary muscle contraction.

“All of these things that we’ve described thus far, sir, from a physiological perspective require some degree of effort and some degree of intent or will, correct?”