If 55 year sentence is on the table, don’t know why he wouldn’t then just roll the dice and take his chances at trial in hopes of having one or more idiots on the jury? He didn’t kill his victim so death penalty wasn’t a concern and he probably wouldn’t have gotten worse than 55 years so even with a public defender he had a fair chance at a better outcome at trial. Maybe he is that rare person who admits his guilt and is truly sorry for his actions and didn’t want to have to put the victim and families through a trial?
He is a sociopath. His admissions of guilt or regret mean nothing. Incarcerating him will save someone’s live later on.
If a 16 YO doesn’t know it’s wrong to kill someone, that person never will.