> The way I understand it, you can analyze it mathematically.
Not meaningfully, for a number of reasons.
> Say one piece of circumstantial evidence puts the likelihood of guilt at 20%/ not guilty at 80%.
Problem with that is that it is rarely easily quantifiable.
> Now another one has a 15/85 ratio. Take that 15% from 80%
This, of course, assumes that the pieces of evidence are independent, which is not necessarily true.
Applying math to the issue isn't really helpful, because that's not the way jurors process evidence.
And if the system were changed to force them to work that way, it would just be a giant mess.