Arizona is a DP state. He Copped a Guilty plea to get LWOP
And it would be my guess that the reason why they offered him a plea deal was the uncertainty involved regarding Loughner's schizophrenia.
It's still an issue for the defense.
The authorities had to force-feed Loughner medication to treat his diagnosed schizophrenia since he's been remanded. While the judge ruled him competent to stand trial, that doesn't mean that the defense wouldn't have pointed to Loughner's condition in an effort to get him exonerated.
Don't laugh -- it happens.
Unfortunately, the taxpayer is stuck with feeding, clothing, housing, and medically treating this scumbag for decades to come.