Example questioning of robbery suspect:
Where did you throw the gun? Come on man, Some little kid is going to find that gun and get hurt.
I threw it in that dumpster over there.
Boom. Admissible as evidence, but you have to stop questioning there, until you Mirandize.
I;m not so sure it’s that important at this point...not with all the evidence they have....the guys going to at minimum get life....might even try to plead insanity and under the control of his older brother.
The larger issue is getting what information they can....because since he is now in custody he’s no longer a threat to public safety.