The trial for the older suspect in the deadly STEM School Highlands Ranch shooting from May 7, 2019 has begun.

Devon Erickson, 20, is accused of helping co-defendant Alec McKinney, 18, carry out the shooting, which left senior Kendrick Castillo dead and eight others injured.

In January 2020, Erickson pleaded not guilty to dozens of charges, including first-degree murder.

Jury selection for the trial, from a pool of 600 potential jurors, began May 24. The trial is set to begin once 12 jurors and four alternates are seated. As of May 26, the final jurors had not been selected. 

MORE: Full coverage of the STEM School shooting and its aftermath

Last year, McKinney, who was 16 at the time of the shooting, pleaded guilty to numerous charges, including murder, and was sentenced to life in prison plus 38 years, with the possibility of parole after 40 years.

If Erickson is found guilty of first-degree murder, there is a mandatory sentence of life in prison without the possibility of parole.

What to know about the trial:

You can watch it live, virtually.

Due to COVID-19 precautions in the courtroom, no members of the public outside of the case will be permitted to be in the courtroom. Instead, those interested in watching can do so via livestream access.

The link to the virtual courtroom, which will change every day, can be found by visiting www.courts.state.co.us then viewing the “courts” menu and selecting “trial courts by county” then navigating to “Douglas County.” At the top of that page, there is a link to view the courtroom. 

The story told by the co-defendant, Alec McKinney, has evolved.

Just after the attack, McKinney told investigators he had planned the shooting and forced Erickson to cooperate. Erickson told a similar story, adding that McKinney had threatened his life if he didn't participate. 

However, prosecutors have worked to poke holes in that narrative, pointing out that Erickson had several opportunities to stop the attack but didn't do so. During his sentencing hearing in 2020, McKinney alleged that he had actually acted under pressure from Erickson.

McKinney may testify.

In a pretrial motions hearing, the prosecution and defense mentioned that McKinney could, at some point, be subpoenaed as a witness for the prosecution.

George Brauchler will lead the prosecution team.

While George Brauchler, the former District Attorney for the 18th Judicial District, officially stepped down from his term-limited position in January, his successor John Kellner asked him to help finish the case.

Erickson will be represented by private attorneys Julia Stancil and David Kaplan.

The trial is scheduled to last until June 25.

After jury selection, the trial will proceed like any other case, beginning with opening statements from the prosecution and defense. Then, the prosecution and defense will each present their cases along with witness testimonies. 

Each side will have the chance to cross-examine the other side's witnesses. Then they will deliver closing statements, followed by jury deliberations. If the jury can reach a unanimous decision, they will announce those verdicts.