After seeing the State of Washington Jury instructions for manslaughter as quoted in this answer https://law.stackexchange.com/a/96079/388, I'm wondering why the instruction is "if... each of these elements has been proved beyond a reasonable doubt, then it will be your duty to return a verdict of guilty" (my emphasis)
Shouldn't it be all of the elements, taken together, rather than each one.
I'm thinking that the more elements there are to a crime the harder it should be to prove. Even if there is no reasonable doubt on any one element, in principle there could be a reasonable doubt when all elements are considered together.
For instance say a juror considers a doubt as a certain probability, and reasonable doubt to be any doubt of more than 1%. Then if they consider the probability that each element happened to be 99.5% they would say they have no reasonable doubt of any element, but by assuming the probabilities are independent and multiplying them they would find that the probability that the entire crime was committed to be only 98.5% and therefore say that they have a reasonable doubt.
Manslaughter is perhaps a bad example, because logically each element could not happen if the previous one did not. But the same logic seems to apply to many other crimes - for instance theft of livestock. It's possible someone took an animal without intending to deprive the owner of it, or that they had the intention but didn't actually take the animal. So if each of these elements is proved but only marginally beyond a reasonable doubt, then it seems that the offence as a whole should not be considered proved.