The murder trial of 20-year-old Joseph Koenig over a rock-throwing death in 2023 began Monday in a Jefferson County courtroom. 

Chief Deputy District Attorney Katharine Decker opened arguments by placing a large rock held in a plastic bag on the railing in front of the jury.

“Frequent, focused and fatal,” she started, describing the action of the three 18-year-old men alleged to be involved in the death of 20-year-old Alexa Bartell on April 19, 2023. “The defendant’s attacks were frequent. The defendant’s targets were focused. The defendant’s weapons were fatal.”

Thomas Ward, one of Koenig’s defense attorneys, countered during opening statements: “(The teens) were not terrorists. They were teenagers.” 

Koenig is charged with one count of first-degree murder, nine counts of attempted first-degree murder, three counts of second-degree assault and six counts of attempted second-degree assault.

Around 11 p.m. the night of her death, Bartell was driving to her girlfriend’s home after being at a friend’s house. Her girlfriend, Jenna Griggs, was on the phone with her before the call went silent.

“(The call) just stopped. It didn’t hang up. It just went silent,” Griggs said on the witness stand Monday.

Griggs quickly turned away as the prosecution flipped through photos of the crash, tears flowing. Bartell’s family cried in the stands, many holding their heads downward.

Koenig, too, held his head low, not making eye contact with Griggs as she turned toward him.

The incident happened near the 10600 block of Indiana Street near Rocky Flats Wildlife Refuge.

Investigators said she was hit by the large landscaping rock placed in front of the jury. The rock, according to investigators, was hurled from a truck driven by Koenig, with friends Zachary Kwak and Nicholas “Mitch” Karol-Chik also in the vehicle.

The rock crashed through the top of the driver’s side part of Bartell’s Chevrolet Spark windshield, hit her in the head instantly killing her, and completely broke out the back windshield before it came to rest on the side of the highway. 

Bartell’s car then drove through a fence and around 200 feet into a nearby field. Griggs noticed that Bartell’s car had entered the field on her GPS and drove to it, finding Bartell dead.

According to Broomfield Police Department Officer Kyle Timmerman, Bartell had no pulse and was already cold upon his arrival shortly after the crash.

The three suspects were arrested around six days after, all facing first-degree murder charges. Both Kwak and Karol-Chik pleaded guilty to less severe charges in plea deals and are expected to testify against Koenig during the trial. The two will be sentenced after Koenig’s trial is over.

The prosecution opened Koenig’s trial arguing that the actions of the three teenagers were targeted, with the group knowing the possible outcomes of their actions — leading to the filing of first-degree murder charges.

Decker claimed that the teens had thrown rocks and other heavy objects from moving vehicles multiple times between February and Bartell’s death — information First Judicial District Judge Christopher Zenisek allowed to be present at the trial in February. 

The first incident, according to Decker, occurred on Feb. 25, 2023, when Koenig and Kwak allegedly threw a rock at a car, smashing the windshield and sending glass into the backseat where a child sat. The car drove off the road.

There were then nine other incidents on April 1 and April 19, including Bartell’s death, in which the teens allegedly threw rocks and lawn ornaments, smashing windshields and front ends of vehicles. 

The 10th victim was Bartell. All of the others are expected to testify during the trial.

“Unlike the others, you will not meet her,” Decker said of Bartell. “Unlike the others, she will not tell you anything, and that’s because of what the defendant purposely did with this rock.”

The defense denied the intent of the act — the overall classification of first-degree murder — claiming that the three were just doing pranks and attempting to “one-up” each other throughout the evening, Ward said, starting initially with harmless pranks like leaving phone numbers on cars and twisting sideview mirrors.

Ward even claimed that the rock throwing that evening started with parked, empty cars, escalating throughout the night.

He said the night initially involved pranks that “teenagers with nothing to do but hang around are prone to do.”

Ward called it reckless, dangerous and “incredibly stupid,” but not first-degree murder.

“He did not knowingly commit a murder. In fact, he did not intend to hurt anyone. In Koenig’s mind, he was not targeting drivers. He was throwing rocks at cars,” he said.

The crux of the trial will be whether or not Koenig had extreme indifference to human life when throwing the rock. If the jury finds that Koenig did, in fact, know that the act could kill someone, a guilty verdict may be found.

If the jury finds that Koenig was just acting recklessly and never intended to harm another person, he may be found guilty of manslaughter — the charge the defense is asking for.

The defense is not arguing whether Koenig was involved in the act, but that he did not mean to harm Bartell.

In fact, the defense argued that the story of who threw the rock that killed Bartell is still up for debate, though it does not truly matter to the outcome of the trial.

Ward claimed that Kwak actually threw the rock, backed up by his ever-changing stories throughout investigations.

Initially, according to Ward, Kwak said that he did not know why he was arrested and did not know where he was that evening. He only admitted that Koenig threw the rock after investigators told him they had proof.

Furthermore, Karol-Chik allegedly told investigators Kwak threw the rock three times throughout various interviews. The fourth time, he said Koenig did it.

Karol-Chik was then offered a “sweetheart deal” two weeks after saying Koenig did it, confirming “the story the prosecution prefers,” Ward said.

Both the prosecution and defense agreed that the thrower doesn’t matter, only the intent does.

Ward claimed all three are guilty, saying, “We are not running from that, but the evidence will show that Alexa Bartell’s death, as tragic as it was, was not first-degree murder.”

The prosecution said Koenig was excited by the act, even cheering when the rock penetrated Bartell’s window. The trio also made a u-turn and took a photo of the crashed vehicle as a memento.

Decker also said Koenig intentionally sped up as he readied to throw the rock, increasing the chances of harm. He also did not call 911 after the crash.

Koenig then allegedly told the other two that they had to “take this secret to the grave. We’re blood brothers, now,” according to Decker.

The defense is expected to bring in adolescent brain development experts to testify that Koenig only threw the large rock because he was experiencing a feeling of “hot cognition,” a state of mind when emotions control the thought process, resulting in risky behavior.

The prosecution said they will not bring any experts to the stand, because “no expert can tell you what the defendant knew when he was committing his crimes,” Decker said.

The prosecution will, instead, bring other victims and the co-defendants to the stand over the estimated two-week trial.

On Monday, Bartell’s mother, Kelly Bartell, was the first to take the stand.

The two lived and worked together prior to Bartell’s death. The night of her death, Bartell had told her mom she was heading to her girlfriend’s work.

“I remember stopping before I went out the door, just having the sense to go back and give her a hug. Something just pulled me that night,” she said, stumbling through the story behind hard tears.

Kelly Bartell detailed the tattoo on her daughter’s arm. The tattoo was Bible passage Luke 6:27, which reads, “Love your enemies, do good to those who hate you, bless those who curse you, and pray for those who mistreat you.”

The trial will continue Tuesday morning.

Former Denver Gazette reporter Carol McKinley contributed to this report.