In one of the more intriguing parts of Petrone's decision, she questioned whether research into the development of adolescents had moved "beyond speculation." 

"There is substantial evidence that adolescents engage in dangerous activities despite knowing and understanding the risks involved," she said in her 32-page decision, written in an unconventional style that included page after page of bullet points. "More research need(s) to be done to take this field beyond speculation."

Petrone also dismissed many of the witnesses who testified about how Davis had reformed in prison. The judge noted that the witnesses had admitted being part of a "cause" for juvenile justice and questioned how much they really knew about Davis.

She called some of them "well-intentioned but uninformed" and said others had "clouded" opinions -- including Abner Mikva, a former federal judge, congressman and White House counsel who testified on Davis' behalf and also expressed his concerns about the punitive nature of the justice system.

"Mikva does not know the defendant and saw him one time in Cook County Jail, for less than an hour," Petrone wrote.

Petrone pointed to several threats Davis was said to have made toward correctional officers and other prison officials and the dozens of prison violations he incurred over the years. She also noted that Davis once impregnated a woman who was visiting him in prison.

The judge acknowledged his troubled background, including that he was raised in an uninhabitable home by an illiterate grandmother who struggled to care for his most basic needs. But she said he had ample opportunity for help growing up.