Matthew Hale might just be the least likely suspect. He's smart enough to earn a law degree so he'd also be smart enough to wait until after sentencing to try something like this. He probably has no chance of ever stepping out of jail now. Also since he's in solitary confinement and prison calls are generally recorded and/or monitored, it would be extremely difficult to organize the attack.
50% odds it's a street criminal. 50% it's a criminal from another case.
I think a more likely option than either of your two is that one of Hale's followers (many of them ex-cons--I think half the "chapters" he claims are prison-based) simply took it on himself to do the job that he knew Hale wanted done. Just as in the Byrdsong shooting spree, Hale's hands are, technically, clean.
The Chicago Tribune today reports that Hale is under the sort of guard that is generally given to terror suspects post 9/11. Visits from his parents twice a month with FBI listening and that's it. This sort of guard for Hale was ordered by John Ashcroft personally.
Or it could be one of his follower's who did this independently, without orders from Hale. Some nutty woman from the Manson family tried to kill Gerald Ford back in the mid-70's; and though she did it in Manson's name, there was never any proof that he asked her to do it.
Another thing; you have to have some intelligence to pass the bar exam; and some state exams are more difficult than others, but it really requires memorizing a lot of case law more than innate brilliance. My husband is a lawyer who passed the NY bar exam, one of the most difficult. A great guy, but no genious. And I've met plenty of lawyers through him, and you'd be surprised how average most of them are.
Just a little observation. No offense meant to lawyers in general.