The jury selection process was set to get underway Monday in Douglas County District Court for the second suspect accused in connection to the May 2019 shooting at the STEM charter school in Highlands Ranch that killed one student and wounded eight others. 

Devon Erickson, now 20, faces more than 45 charges, including first-degree murder and attempted murder. He has pleaded not guilty and faces a mandatory life sentence if convicted on the murder charge.  

The shooting killed 18-year-old Kendrick Castillo. Alec McKinney, 16 at the time of the shooting and now 18, pleaded guilty last year to charges including first-degree murder and attempted murder. He received a life sentence plus 38 years, with the possibility of parole.  

A security officer at the school wounded two students when he fired his gun during the shooting. Although he was not supposed to be carrying a gun as part of his contract, he has not been charged for wounding the students.  

Erickson and McKinney have implied the other was the driving force behind the shooting. 

During a hearing Monday, Erickson’s defense attorneys indicated they hope to cast doubt on McKinney’s credibility as a potential witness in Erickson’s trial, saying he has changed his story. 

In Monday morning’s hearing, Judge Theresa Slade agreed to limit the defense’s use of evidence about Erickson’s mental condition. 

She cited a Colorado Supreme Court decision from earlier this month that precludes evidence in a criminal case that tends to prove insanity if a defendant isn’t asserting an insanity plea. Insanity has a legal definition that relates to a defendant’s ability to tell right from wrong at the time they committed an act, and it’s possible for a defendant to be mentally ill but legally sane. 

Slade and the attorneys referenced reports by experts who examined Erickson, indicating they contain discussion of factors that speak to Erickson’s mental condition such as auditory hallucinations, drug use and sleep deprivation.  

Jury selection could take several days. In a criminal case when the defendant faces a prison sentence, each side can dismiss up to five potential jurors without cause. But each side gets unlimited challenges for cause to boot jurors for issues including bias. 

George Brauchler, formerly the 18th Judicial District attorney who termed out of office in January, has stayed on as a chief deputy district attorney to oversee prosecution of the case. 

The Associated Press and 9News contributed to this report.