Closing arguments were given Friday in the trial of a South Florida teen charged in the brutal attack on Josie Ratley.
They claim Treacy suffered from post-traumatic stress disorder and was not in control of what he was doing at the time of the March 17, 2010 attack on Ratley.
Prosecutors say Treacy was in his right mind and knew exactly what he was doing when he attacked her.
"We know, no doubt, that Wayne Traecy has experienced a really traumatic event," prosecutor Maria Schneider said Friday.
She added, "But you know what, again, there are millions and millions of people who experience horrific things, one horrific thing, and don’t go out and kill others."
Psychiatrist Dr. Alexander Neumeister, one of the world's foremost experts on post-traumatic stress disorder, testified for much of the day Thursday. He gave the jury a tutorial on the brain and on which parts may be affected by PTSD.
Police said Treacy sought out Ratley, who was 15 at the time, after she sent him text messages about his older brother, Michael, who had recently committed suicide. Prosecutors said he punched, kicked and stomped her head with steel-toed construction boots at a bus stop outside Deerfield Beach Middle School.
Ratley suffered severe brain damage in the attack and spent over 40 days at the pediatric intensive care unit at Broward General Medical Center.
"At the time of the attack on the girl, Wayne had severe PTSD, major depression, and he was in the midst of a dissociative episode," said Neumeister, who examined Treacy twice, putting him through a battery of psychiatric exams.
Defense attorney Russell Williams urged jurors to consider a verdict of not guilty by reason of insanity on Friday.
"She did not know that the person that she was picking on was the person that was suffering from severe, chronic post-traumatic stress disorder because he saw his brother hanging from a tree," he said, referring to Ratley.
The jury is expected to get the case on Monday.
Treacy, who faces an attempted murder charge, has been held without bond since the attack. He faces up to 50 years behind bars if convicted.