He absolutely has to have help!
Think of this, in “Bridge of Spies”, they showed how Rudolph Abel, the Soviet spy, when uncovered, was given legal counsel, because it was American system. That lawyer, James Donovan, was instrumental in keeping Abel, as “exchange material”.
It is a very American way, and it has to be done. Moreover, with all small-town and flyover-state idiosyncrasies, the LE did a very good thing. Caught a killer who did a nasty thing and had no witnesses to his crime. Few can boast it. So if it is their killer, and they can prove it (I think they can), they need to have the best lawyer and triumph.
You have to understand, even if he walks free on some technicalities, but the affidavit looks convincing, RA doesn’t walk far. MOO. No one likes their children killed. He is safer in jail.