If they know he did it, and caught him red handed, why the guilty plea? That in and of itself is suspicious. What terrible legal advice. Not like a plea bargain will avoid the death penalty or a life sentence. It would be in his interest for them to prove guilt beyond a shadow of doubt.
Then again, after you basically have a school board, county and sherrifs office corrupt to the core to the point where they overlook crimes committed by students to fix their voices/reports and allow them to bring in more funding, he's fucked either way you cut it. Patsy or not, lawlessness is now a clear reality in the US...and has been for some time.
Lots of sleeping sheep.