Youshock faces four felony counts for his alleged actions -- two counts of attempted murder and two counts of exploding a destructive device with the intent to murder.
Prosecutors allege that Youshock went to the school intending to kill his former chemistry teacher, bringing with him homemade pipe bombs, a Samurai sword and a chainsaw he nicknamed "Collie," after Columbine High School, the site of the infamous 1999 massacre.
But defense attorney Jonathan McDougall on Wednesday refuted the prosecution's assertion that Youshock methodically premeditated his attack on Hillsdale High.
McDougall argued that if it were not for Youshock's schizophrenia, he would not have responded to his teachers' reasonable efforts to get him to do his homework and participate in class by concocting a farfetched plan to murder them.
Deliberations will continue on Monday.