Kendrick Castillo ...

Provided by Maria Castillo via Instagram

Kendrick Castillo

Defense lawyers for accused STEM School Highlands Ranch shooter Devon Erickson began their case Thursday with testimony from a University of Colorado Boulder professor who said the shot that killed Kendrick Castillo might have been unintentional.

The three students who rushed and tackled Erickson just as he pulled the handgun on his British literature classmates probably caused a number of involuntary muscle reactions that caused him to pull the trigger, killing Castillo, Professor Roger Enoka testified.

“I think the speed with which they responded may well have contributed to a startled response,” which was gripping the handgun tightly in reaction to that, Enoka testified.

In the second week of his first-degree felony murder trial, Erickson, 20, on Thursday earlier listened to former classmate Joshua Jones describe how he was shot twice in the leg as he wrestled Erickson to the ground with Brendan Bialy. Castillo was already shot.

The prosecution rested its case and defense attorneys David Kaplan and Julia Stancil began offering their theory about the May 2019 shooting.

Enoka, in testimony about how the body reacts to certain situations and stimuli, suggested that muscles in Erickson’s hand could have pulled the trigger involuntarily in reaction to the rush. He said it was likely certain that being startled by them would have caused him to involuntarily pull the trigger.

Previous testimony revealed Castillo was likely shot by the first discharge from the firearm. He was the first to rush Erickson as he pulled a handgun from a guitar case and demanded that classmates not move.

“If you’re startled, every (firearm) discharge will be unintentional,” said Enoka, the former chair of the Department of Integrative Physiology at CU Boulder and director of its Neurophysiology of Movement Lab.

Under cross-examination by Chief Deputy District Attorney Christopher Gallo, Enoka said it was possible that Erickson was not startled by the rushing students and, therefore, there might not have been an unintentional reflex to them.

Erickson fired the handgun at least four times before Bialy and Jones pried his fingers from it and pinned him until police arrived.

The defense began its case after Douglas County District Judge Theresa Slade first denied a defense motion to dismiss at least 30 of the charges against Erickson, including one of the first-degree felony murder charges and the charges tied to injured students in a different classroom. Slade ruled prosecutors have offered enough evidence for a reasonable juror to make a decision.

Prosecutors have tried to show that Erickson, despite his assertions to police that co-defendant Alec McKinney threatened and forced him into the shooting, ignored numerous opportunities to warn others about it.

McKinney, 18, pleaded guilty to felony murder and more than a dozen other charges related to the May 7, 2019, shooting and was sentenced to life in prison plus 38 years. Because he was a juvenile at the time, by law he is eligible for parole after 40 years.

Erickson, however, faces life in prison without the possibility of parole if convicted on any of two felony murder charges he faces, and a lengthy prison term if convicted on more than three dozen other charges.

Before ending its case, prosecutors showed a video of Erickson’s interview with police just after the shooting in which he repeatedly said McKinney threatened to kill him and others if he did not participate.

Detectives, however, said downloads of the pair’s Instagram and Snapchat messages show that didn’t happen and, in fact, the two confirmed there was a plan between them.

McKinney earlier testified how the two agreed to place the blame on him – avoiding text messages that would have shown otherwise – and that Erickson was to shoot McKinney in order to come off as the hero. That would happen only after the two had killed all the students in the classroom, leaving no witnesses to who actually did the shootings.

The defense is expected to continue its case Friday. They have said Erickson was a troubled teen who was easily misled and manipulated by a homicidal and mentally unstable McKinney.