Joe Koenig — facing a first-degree murder charge in the rock-throwing death of Alexa Bartell — announced Tuesday he would not testify in his trial.

Jefferson County District Judge Christopher Zenisek advised Koenig, 20, of his right to testify before the jury had been brought into the courtroom.

Zenisek told Koenig it was his right to testify — and his right not to.

When Zenisek asked Koenig if he had made a decision, Koenig replied: “Yes, I won’t be testifying.”

Koenig is accused of hurling a nine-pound rock out the driver’s side window of a pickup he was driving the night of April 19, 2023. That rock crashed through the windshield of Bartell’s oncoming car, hit her in the head, and killed her instantly.

He and two others involved in Bartell’s death, Nicholas “Mitch” Karol-Chik and Zachary Kwak, were 18 years old at the time.

Prosecutors rested their case on Friday after calling 51 witnesses — including two others who were with Koenig when Bartell died and were involved in a series of similar incidents that same night.

Koenig’s attorneys, Tom Ward and Martin Stuart, began their case Tuesday by calling Laurence Steinberg, a professor at Temple University and an expert on adolescent brain development.

Steinberg testified that adolescents, which he described as people between 10 and 20 years old, are “inherently more likely to be involved in risky and reckless behavior.”

“That’s true for reckless driving,” Steinberg said. “It’s true for unprotected sex. It’s true for crime. It’s true for unintentional drownings. It’s true for self-inflicted injury, like cutting. It’s true for binge drinking. It’s true for experimentation with illicit drugs.

“So, this is a time of life that is inherently more likely to — to be involved with risky and reckless behavior.”

Koenig faces 19 separate charges:

• One count of first-degree murder for Bartell’s death.
• Nine counts of attempted first-degree murder for other incidents in which rocks or other objects were thrown at oncoming cars on Feb. 25, 2023, April 1, 2023, and April 23, 2023 – the night Bartell died.
• Three counts of second-degree assault for injuries suffered by three of those whose vehicles were hit by thrown objects.
• Six counts of attempted second-degree assault for other attacks in which the victims weren’t injured.
• The first-degree murder charge alleges that Koenig killed Bartell “under circumstances evidencing an attitude of universal malice manifesting extreme indifference to the value of human life generally …” and that he engaged in “conduct which creates a grave risk of death to a person, or persons, other than himself …”

Koenig’s attorneys have suggested that he and his companions were engaged in behavior that was reckless, to be sure, but that they didn’t intend for anyone to get hurt. They suggested Koenig is guilty of a much-less serious crime, manslaughter.

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