Fun fact: judges in England and Wales no longer tell juries that the prosecution needs to have established guilt beyond reasonable doubt. They tell the jury that they need to be sure of the guilt of the accused. The standard of proof has not changed, but surety is meant to be a simpler concept for the jury to grasp than beyond reasonable doubt.
I find this odd. It is, I think, meant to help juries understand that they can convict when it is one person's word against another's. In other words, they are saying to the jury 'you can just believe the victim'. It has to be right that the facts can have been established even when two different versions are presented. You can always tell a story about what happened (or deny everything) but it be clear that you are lying. In everyday life, we would say, 'I'm sure that she is telling the truth'. The problem is that the doubt creeps in when you are asked, 'are you sure?'
Being sure is a psychological state. I am aware that I can be sure of something, that I left my keys on the side, and be wrong about how things are, my keys are not where I'm sure that I left them. Being proved beyond reasonable doubt is a fact about how things are in the world. Her version is established because it is clear and coherent. His version is preposterous.
It seems to me that asking a jury to be sure is likely to result in the jury concluding that they are not sure simply because they can imagine being wrong. That would be a much higher threshold than concluding that they have no good reason to think that they are wrong





