Trial opens for suspect in Jeffco rock-throwing spree that killed Alexa Bartell

GOLDEN — Jefferson County Chief Deputy District Attorney Katharine Decker set a bagged rock about the size of a cantaloupe in front of the jury with a heavy thump Monday.

This rock, she told the jurors, is the rock that killed 20-year-old Alexa Bartell. The defendant, Joseph Koenig, threw it through her windshield two years ago and he is guilty of murder, Decker said during opening statements in Koenig’s jury trial.

“This rock blew through her head like a cannon,” she said.

Koenig is guilty, his attorneys conceded in their own opening statements — but not of first-degree murder. The then-18-year-old didn’t intend to hurt anyone that night, defense attorney Thomas Ward said. He and two other teenagers didn’t think at all about the potential danger of hurling rocks at other drivers. They thought only about hitting cars, not people.

“All three of the boys in that truck are guilty of causing Alexa Bartell’s death,” Ward told jurors. “We are not running from that. But the evidence will show Alexa Bartell’s death, as tragic as it was, was not first-degree murder.”

Koenig’s jury trial started Monday in Jefferson County District Court, where the 20-year-old is charged with first-degree murder, nine counts of attempted murder, three counts of assault, six counts of attempted assault. He faces life in prison if he is convicted of first-degree murder.

Ward suggested jurors should find Koenig guilty only of the lesser offense of manslaughter.

Koenig is accused of carrying out a spree of attacks in which he and two other teenagers threw rocks and objects at passing cars, including one attack on April 19, 2023, that killed Bartell. Koenig and other teenagers threw at least 10 objects at cars on at least three different nights between February and April 2023, prosecutors allege.

“The defendant’s attacks were frequent, the defendant’s targets were focused, the defendant’s weapons were fatal,” Decker said.

She showed photos of cars damaged in the spree. Some had rock-sized holes in their windshield, or smashed bumpers or crushed side mirrors.

Prosecutors say Koenig threw the rock through Bartell’s windshield as the two vehicles passed each other around 10:45 p.m. on Indiana Street near the Rocky Flats National Wildlife Refuge. Koenig’s defense team alleges it was another teenager in the car who threw the fatal rock.

Legally, all three teenagers can be held convicted of causing Bartell’s death regardless of who threw the rock, both prosecutors and defense attorneys told jurors.

Koenig’s is the only case to go to trial. The other two teenagers in the car that night have pleaded guilty and are expected to testify during Koenig’s trial.

Nicholas “Mitch” Karol-Chik, 20, pleaded guilty to second-degree murder and attempted first-degree murder in 2024 and faces up to 72 years in prison. Zachary Kwak, 20, pleaded guilty days later to assault and attempted assault and faces between 20 and 32 years in prison.

Neither Karol-Chick nor Kwak have been sentenced; their sentencings are set for early May. Their plea deals are contingent on their cooperation with Koenig’s prosecution.

All three teenagers were arrested after cellphone data tied them to the crime scene. All were 18 at the time. The trio treated the attacks like a game, court records show. They turned around to take a photo of Bartell’s smashed car as a memento, prosecutors said.

“As the defendant literally blows her brains out, he whoops,” Decker said. “He says ‘Holy (expletive)’ as this rock deposits part of her brain tissue on the side of the road.”

Ward told jurors the teenagers threw rocks at cars after a night of ongoing pranks that escalated from shoplifting and throwing rocks at parked cars to throwing rocks at moving cars as the teenagers tried to one-up each other.

“It was stupid and immature, but not one of these three boys thought that they would use the rocks to hurt people,” Ward said. He called the first-degree murder charge “inflated.”

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