Not an expert but think it through (for US law): only prosecutors have the discretion to decide whether to bring charges and the severity of the charges they wi

Not an expert but think it through (for US law): only prosecutors have the discretion to decide whether to bring charges and the severity of the charges they will bring. A LEO who says to you that they'll get you a better deal if you talk now is lying to you - which not only are they allowed to do, it's in their training to do so (specifically, investigators are trained to tell you what you need to hear to get you to cooperate). They don't have the authority to waive the rights and privileges of the prosecutor's discretion.