Jasper, dead people arent supposed to say their finds and thoughts after they died as you did man, gives advantages to the living (and the chaos it causes is the natural consequences, dead setting things straight ruins that), they can use information you gave them before your death, not after, and you being detective, even more vital (as in you saying who you investigated, thats the perk of killing you, they stop your information flow), dont give any more hints and confirmations of what was said (gives leeway to manipulate).
And I seen wtf cases, but never a detective who pretends to be the crooked cop

Much easier to just pretend to be a normal civilian, you know, something that wont get you hanged?
P.S Ze, Sab was just a normal civilian??? (not jailer??).