Pardon my limited, Law & Orderesque knowledge here - I imagine this will be a can of corn for the attorneys, but…
…in watching those types of shows, the detectives routinely lie in interrogation rooms to the perp about things - like that there’s evidence that can prove his guilt when there really isn’t, or that the other guy in the other interrogation room just fingered him as the ringleader, etc.
Can one detective come into the room, say they’re with the DA’s office and say they’ll consider a plea, just to get the guy to confess? Is this different from being “undercover” so to speak?
I’m always amazed by the “we have a verbal deal” type bargaining that goes on with the attorneys anyway, so a detective saying “yeah, I’m with the DA’s office, go ahead” doesn’t seem like too much of a stretch to me.