I mean, it's one thing when talking about a misdemeanor or a fine (the case isn't worth further challenge but I still believe I am innocent of the charge) but murder with a blade? Decapitation?
If the plea is substantially true, it should be admissible. I can imagine a situation where I am completely innocent but the prosecution has a hundred witnesses who are certain it was me and I can’t produce any exculpatory evidence. I recognize that the state has sufficient evidence yo convict me.