Teen, Joseph Koenig, Convicted of Murder For Dropping Boulders Off Busy Overpass
Jurors in Jefferson County needed barely two hours Friday morning to convict Joseph Koenig of first-degree murder for hurling a landscaping rock through the windshield of Alexa Bartell’s moving car, killing the 20-year-old as she drove near Arvada in April 2023. Deliberations began late Thursday and resumed at 9 a.m.; by 10:45, the panel had returned guilty verdicts on every one of the 19 counts Koenig faced.

Koenig, now 19, stood accused not only of Bartell’s murder but of unleashing a late-night rock-throwing spree that terrorized motorists across northwest metro Denver. Prosecutors charged him with nine counts of attempted first-degree murder for the other cars struck, three counts of second-degree assault, and six counts of attempted second-degree assault.

While the jury found Koenig guilty on each allegation, several counts were reduced under Colorado law.

Last week jurors heard from nearly two dozen witnesses, including victims who recalled the sudden shatter of glass and the panic of losing control at highway speed. The most damning testimony came from Koenig’s two friends—Nicholas “Mitch” Karol-Chik and Zachary Kwak—who took plea deals and told the jury Koenig threw the fatal rock. The defense pounced on Karol-Chik’s earlier statement to police suggesting Kwak hurled the final stone, but both men insisted on the stand that Koenig was responsible for Bartell’s death.

Koenig himself never testified. Instead, defense lawyers called Laurence Steinberg, a Temple University adolescent-brain researcher, to argue that impulsivity and Koenig’s ADHD lessened his culpability. Deputy District Attorney Katharine Decker countered in a pointed cross-examination, pressing Steinberg to acknowledge that teenagers can still foresee lethal consequences. Koenig was a high school senior at the time of the incident.

Originally scheduled for trial last summer, the case was postponed for a court-ordered mental-health evaluation after Koenig’s attorneys cited an ADHD diagnosis and borderline personality disorder. Closing arguments Thursday distilled the stakes: prosecutors said Koenig acted “knowingly and intentionally,” while defense attorney Martin Stuart asked jurors to convict only of reckless manslaughter—calling his client “guilty of a crime, but not murder.”

Evidence showed that Koenig, Karol-Chik, and Kwak circled back to the crash scene on April 19, 2023, photographing Bartell’s disabled Chevy Spark instead of checking on her or dialing 911. That callous post-attack behavior, prosecutors argued, underscored Koenig’s indifference to human life.

After the verdict, Bartell’s mother, Kelly, stood outside the courthouse clutching a framed photo of her daughter. “These have been the hardest two years of our lives, but we got justice today,” she said through tears. “It doesn’t bring Alexa back, and that’s horrible. But we hope no family ever has to live this nightmare again.”

District Court Judge Mark Randall set Koenig’s sentencing for June 3 at 8:30 a.m. Victims and relatives will be allowed to address the court before penalties are imposed; a first-degree murder conviction in Colorado carries an automatic life sentence with the possibility of parole after 40 years.

Karol-Chik and Kwak, who pleaded guilty last year to lesser charges—including second-degree murder and multiple counts of attempted assault—are scheduled to learn their fates on May 1 and May 2, respectively
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