Defense for Jeffco rock-throwing suspect focuses on teenage brain development

The defense attorneys for one of three teenagers accused of killing a driver during a rock-throwing spree in Jefferson County two years ago opened their situation Tuesday with a focus on how teenagers brains differ from adults Alexa Bartell Provided by Jefferson County Sheriff s Department Jospeh Koenig who is now but was at the time of the spree is standing trial on charges of first-degree murder nine counts of attempted murder three counts of assault and six counts of attempted assault He is accused of throwing a -pound rock into the windshield of a passing car on April killing the driver -year-old Alexa Bartell The fatal attack was one of several times Koenig and two other teenagers threw rocks at cars that night Koenig s attorneys have presented his actions during the rock-throwing spree as thoughtless teenage behavior rather than first-degree murder They admitted he is responsible for Bartell s death but argued he should be ascertained guilty of the lesser charge of manslaughter First-degree murder carries a mandatory life prison sentence Laurence Steinberg a professor of psychology and neuroscience at Temple University testified as an expert for the defense Tuesday that young people s brains continue to develop into their early s and that adolescent brains differ from adult brains in several key options Adolescents are more impulsive than adults more focused on the rewards and short-term consequences of decisions than the downsides and long-term consequences and are more susceptible to the influence of peers than adults Steinberg testified Adolescence is a time when the accelerator in the brain is pushed down to the floor that is the limbic system but there is not yet a good braking system in place That is the prefrontal cortex Steinberg testified Research shows that people between the ages of and can at times think and act like adults but are more likely to think and act immaturely like younger teens when they are experiencing heightened emotions and when they are with their peers Steinberg testified The atmosphere inside the truck on the night of the fatal rock-throwing spree in which then- -year-olds Nicholas Mitch Karol-Chik and Zachary Kwak were cheering and encouraging each other to throw rocks would create that heightened emotional state and likely compromise the teenagers decision-making Steinberg testified Related Articles Teen whooped with excitement after throwing fatal rock in Jeffco spree second accomplice testifies Teens drove mph before fatal throw in Jeffco rock-throwing spree accomplice testifies Trial opens for suspect in Jeffco rock-throwing spree that killed Alexa Bartell Rock-throwing individuals turned back to take photo of fatal crash as memento Jeffco affidavit says On cross-examination the professor admitted that individual brain advance differs and certain -year-olds are more mature than others He also acknowledged that research on the brain has evolved over the last couple of decades and that selected studies have contradicted certain findings on adolescent brains The defense occurrence opened Tuesday after prosecutors with the Jefferson County District Attorney s Office rested their scenario late Friday The trial did not take place on Monday The defense expert s testimony follows testimony from the two other men who were in the car that night who both pleaded guilty and agreed to testify against Koenig as part of their plea agreements Karol-Chik pleaded guilty to second-degree murder and attempted first-degree murder in and faces up to years in prison Kwak pleaded guilty days later to assault and attempted assault and faces between and years in prison Both are scheduled to be sentenced in early May Sign up to get crime news sent straight to your inbox each day