In his sentencing, as transcribed by GamePolitics, Lorain County judge James Burge intimated that he believes -- "as a human being ... and not a jurist" -- that gaming can elicit similar physiological responses and addictions as some drugs. He further decried the creation of a delusional environment. The quote that's currently making the rounds is, "I firmly believe that [Petric] had no idea at the time he hatched this plot that if he killed his parents, they would be dead forever." In other words: Petric didn't realize there are no respawns in real life, according to Judge Burge.
Of course, attributing Halo 3 as a causation of these crimes is probably reaching, especially when most of the other 6.4 million who bought the game seem to be of sound mind. I'm no psychologist, but to me it seems this is about the wrong mind and the right catalyst inciting the most heinous of actions -- whether it be Master Chief, Niko Bellic, The Beatles, or a German Shepherd.
Judge James Burge sentenced the boy to 23 years to cries of mercy from the boy's surviving father, who stated that Daniel "still does not understand why he did something so terrible."
Daniel's sentence is actually a lot lighter than it could have been, as the prosecution was pushing for the maximum sentence of life without parole. The defense's argument was that Daniel was so young and so addicted to the game that he could not be held accountable. Petric, only 17 years old, was even younger when he committed the crime, and the judge's lenience is likely tied to his belief that young Daniel was addicted to the point of delusion.