As for plea bargains, I accept what you say: the judge decides upon the sentence once a crime is proved. But isn't the prosecution then practising some kind of deception on the accused: offering a deal they can only ask for? No, wait. It's surely in the power of the prosecution to offer only sufficient evidence to convict on the lesser charge if they want to, especially in adversarial systems like America's or ours. That makes it perfectly possible for the prosecution to make sure the bargain is honoured.