Opening statements got underway Monday morning in the trial of one suspect accused in the 2023 rock-throwing incident that killed 20-year-old Alexa Bartell. Juror selection was completed on Friday for the expected 11-day trial o f Joseph Edwin Koenig.In opening statements, the prosecution described Koenig's actions as "frequent, focused and fatal." These are the three things, the prosecution, said this case comes down to.Koenig, 20, is accused, alongside Zachary Kwak and Nicholas Karol-Chik, of throwing rocks at cars in the areas of Jefferson and Boulder counties, resulting in Bartell's death. Bartell was driving on Indiana Street in Jefferson County at approximately 10:45 p.m. on April 19, 2023, when a landscaping rock struck her windshield. She was pronounced dead at the scene."The defendant wasnt dropping rocks off bridges. He was driving either his truck or his friends truck, and throwing them at oncoming drivers," Katharine Decker with the Jefferson County District Attorney's Office said during opening statements. "Those speeds and velocities, creating enough force to smash through windshields, destroy the bodies of cars, destroy the bodies of humans."Decker continued her opening statements by pointing to Koenig's involvement in ten total instances of rock throwing, over the course of three separate nights as evidence the crimes were "frequent." The prosecution told the jury, they would hear from the victims of those nine other incidents throughout the course of the trial. The People alleged Koenig's targets were "focused" on drivers of passing cars, although the defense later countered that Koenig and his friends did not intend to hurt anyone. The prosecution also said the weapons Koenig used were fatal. He was not throwing snowballs, eggs or bottles; the People showed the jury the large landscaping rock that killed Alexa Bartell. During opening statements from Koenig's defense, Martin Stuart did not dispute Koenig was involved in the rock-throwing incidents. "This case is not about avoiding accountability for Joe Koenig. At the end of this trial, we're going to ask you to hold Joe Koenig accountable," Stuart said, "of the crime he actually committed manslaughter." The defense described Koenig's actions as reckless, dangerous and catastrophic, but not first-degree murder. About a week after Bartell was killed, all three defendants, who were 18 years old at the time, were arrested and each charged with first-degree murder, attempted murder and assault-related charges.Koenig pleaded not guilty to the charges in April 2024, but Kwak and Karol-Chik took plea deals. Kwak, 20, pleaded guilty to two counts of second-degree assault and criminal attempt to commit second-degree assault. Karol-Chik, 20, pleaded guilty to second-degree murder and attempted first-degree murder. Kwak and Karol-Chik face prison sentences of up to 32 and 72 years, respectively. Their sentencing will take place after the conclusion of Koenig's trial. As part of their plea deals, Kwak and Karol-Chik are set to testify at Koenig's trial. During opening statements, the prosecution and defense brought up differing evidence as to who threw the rock that ultimately killed Bartell. The prosecution told the jury, they would hear evidence that Koenig rolled down the driver-side window and threw the rock with his dominant, left hand. However the defense pointed to past interviews with Karol-Chik, stating Kwak was the one who threw that rock. The prosecution said their focus of the trial is to prove the defendant was at least complicit in Bartell's death, that Koenig aided and abetted. The People told the jury they don't have to prove Koenig's intent, premeditation or deliberation. While the defense plans to call an expert witness to testify to the psychological development of late adolescents like Koenig, Kwak and Karol-Chik, the prosecution told the jury that no one can verify what the defendant knew during the rock-throwing incidents.The defense disagreed, saying the circumstances of being 18 years old is important because scientific research has determined certain brain areas are not fully formed at that age. The area responsible for self regulation, ability to control behavior, thoughts and emotions aren't completely development, Stuart said. People between 18 and 21 years old are more impulsive and susceptible to peer influence and risky behavior. "We dont convict people in Colorado of the most serious crimes without proof of a state of mind," Koenig's lawyer said. Stuart said Koenig did not knowingly commit murder, that the three teenagers had no reason to know anyone was hurt. "He was throwing rocks at cars, as foolish as that sounds," Stuart said.Koenig's defense described seniors in high school with nothing else to do, arguing there wasn't a plan to vandalize property or cause chaos. The events escalated from shoplifting Starbursts at Walmart, too putting other people's phone numbers under random cars' windshield wipers, to throwing rocks at parked cars before ultimately hitting oncoming drivers. Stuart classified the agreements that Kwak and Karol-Chik reached with the prosecution as "sweetheart deals," and put the onus on all three teenagers in this case. "All three of these boys were on the same joyride. All three threw rocks from the truck. All three egged each other on and cheered when a rock hit a car. Each time a rock was thrown, including the last time, all three aided and abetted. All three boys in that truck are guilty of causing Alexa Bartell's death," the defense said. None of them spoke up to stop the activity, or pause what they were doing to consider the consequences, according to the defense. Prior coverage: What makes trial different for suspect in 2023 rock throwing that killed 20-year-old Alexa Bartell Trial begins for Joseph Koenig, accused in Jeffco rock-throwing incident that killed Alexa Bartell Trial for third suspect in rock-throwing case delayed after judge orders mental health evaluation Second teen accused in Alexa Bartells rock-throwing death pleads guilty One of three suspects in rock-throwing death of Alexa Bartell pleads guilty Alexa Bartell case: Suspect in rock-throwing crimes now facing more charges Alexa Bartell's family celebrates life of 20-year-old killed 1 year ago in rock-throwing crime Teens charged in deadly rock-throwing spree that killed Alexa Bartell will face trial Teen suspects in rock throwing killing of Alexa Bartell to face first-degree murder, assault charges ...read more read less