JEFFERSON COUNTY, Colo. — The man accused of throwing a rock at a Jefferson County driver in 2023 and killing her will not take the stand in his own trial.
Joseph Koenig is facing several charges for the 2023 incident in Jefferson County, including first-degree murder of 20-year-old Alexa Bartell.
All three defendants in this case — Koenig, Zachary Kwak, 20, and Nicholas Karol-Chik, 20 — were 18 years old at the time of the crimes, and were charged with first-degree murder, attempted murder, second-degree assault and attempted second-degree assault.
Koenig pleaded not guilty to first-degree murder, as well as multiple counts of attempted first-degree murder, second-degree assault and attempted second-degree assault in April 2024.
His two co-defendants both took plea deals. Kwak pleaded guilty to two counts of second-degree assault (causing injury with a deadly weapon) and criminal attempt to commit second-degree assault. Karol-Chik pleaded guilty to second-degree murder, attempted first-degree murder and a crime of violence sentence enhancer added to the second-degree murder charge. All other charges against the two men were dropped.
Read our previous coverage of the trial in the stories below
- Trial begins for Joseph Koenig, accused in Jeffco rock-throwing incident that killed Alexa Bartell
- Opening statements begin for trial of suspect in Jeffco rock-throwing incident that killed Alexa Bartell
- Prosecution expected to rest its case in Alexa Bartell murder trial by end of week
- Rock-throwing case: Co-defendant testifies against Joseph Koenig in Jeffco murder trial of Alexa Bartell
- Second co-defendant testifies against close friend on trial for murder of Alexa Bartell in Jeffco
On Tuesday, the judge informed Koenig of his right to testify. Koenig replied that he would not be testifying in his trial.
The majority of Tuesday's testimony came from Dr. Laurence Steinburg, a professor of psychology with a specialty in adolescence and young adulthood psychology who was called by the defense.
Throughout the trial, Koenig's attorneys have asserted that while he was legally an adult at the time of the crime, Koenig's brain had not fully developed. Dr. Steinburg testified that an 18-year-old brain might not be fully developed in terms of self-regulation or impulse control.
"Adolescents tend to overweight the potential rewards of a decision — what good that's going to happen to me if I do this — and underweight the potential of bad consequences of a decision — what could go wrong? How could I or someone else be hurt?" said Steinburg.
During a lengthy cross-examination by the prosecution, Steinburg was questioned about his credibility. He also acknowledged that teens and young adults do have the capacity to assess risk and can control their behavior.
"Are you telling this jury that adolescents cannot control their impulses?" asked the prosecutor.
"No, I didn't say that, and I'm not telling a jury that," Steinburg responded.
"So, can adolescents control their impulses?" she asked.
"They can, yes," he responded.
"Can they stand up to peer pressure?" she asked.
"Yes," he responded.
In the final hour of the day, the jury heard testimony from Dr. Alexandra Lynch, who gave Koenig a mental health evaluation. She testified that Koenig exhibited symptoms of moderate attention-deficit/hyperactivity disorder (ADHD) and had previous records diagnosing him with the disorder. She also observed borderline personality disorder, which she explained can be associated with reckless behavior.
"Is it possible that, based on those opinions, that Mr. Koenig's inattentive type diagnosis also contributed to impairments at the time of the alleged offenses?" Koenig's attorney asked. "Is your opinion that that's possible?"
"Yes," Lynch responded. "There's certainly diagnostic overlap between ADHD and borderline personality disorder in the realm of impulsivity. So it would be clinically impossible for me to, with 100% certainty, hang my hat on one over the other. I said that it was more likely, in my clinical opinion, that the borderline contributed, but the full reality is that it's likely that there are multiple factors at play — borderline personality disorder, ADHD, as well as having the brain of an adolescent."
During cross-examination, the prosecution pressed Lynch on that.
"ADHD is not the worst thing that someone can have as a diagnosis?" the prosecution asked. "Correct, sure," Lynch replied "In fact, a lot of people have it." "Right. Yes." "About 5% of the US population has it." "Yes." "People with ADHD can be high functioning?" "Absolutely."
Cross-examination is expected to continue on Wednesday.
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