The Burden of Proof is a concept which has caused much controversy! It has many meanings. Here are some brief thoughts on it's everyday usage.
Everyday Usage
For most of us, I'd guess that when we hear "Burden of Proof", we'd think of our legal system and the concepts that apply in criminal law. As I understand it, in that area there's two main guiding principles. Firstly, one is "Innocent until proven guilty" and secondly, they must be proven guilty "beyond a reasonable doubt".
Considerations
This raises all kinds of issues. Here are two: Firstly, the presumption of innocence (the first principle) means that the evidence for guilt must be shown and tested. Without being able to prove guilt, the defendant remains innocent. Being charged doesn't mean that the person being charged is guilty unless they can prove their innocence. No! It means the prosecutors must find enough evidence and then show they are guilty. Secondly, not only must evidence be found but that evidence must get to a certain level. It's effectively about proof, not probability. Some amount of evidence could perhaps show probability, but that wouldn't be enough. Sometimes it might seem very probable that the defendant is guilty, based on the evidence we do have, but unless the evidence is strong enough to put any possible reasonable doubts to bed they must remain innocent under the law.
A Current Example
A recent example (albeit, not in criminal law) might be the Essendon Bombers supplements case. This is an ongoing investigation and no players have yet been issued with any infraction notices. It has been speculated in both major Melbourne newspapers that part of the reason why players have not been charged is because Essendon's record keeping and governance was so poor. This line of thought is suggesting that ASADA just couldn't prove which players took what because of a lack of paperwork and lack of knowledge from the players about what they were taking. Nonetheless, it is possible that ASADA investigators consider it probable that Essendon players took illegal substances but that they simply don't have enough evidence.
The Big Picture Application/Analysis
As a side note and a thought experiment, consider this: If that were the case and it seems probable that the players were guilty but that the evidence wasn't strong enough to convict any individual Essendon player, would it be reasonable for them (or us, if we had the evidence too) to believe that the Essendon players took illegal substances (putting aside the issue that them personally believing it has nothing to do with whether they charge them)? In other words, looking at the big picture: If we have some evidence but we are lacking other evidence, it is reasonable to hold a belief based on an interpretation of probability about where the current evidence points? If so, how much evidence do you need? Does it depend on what kind of situation or example you're considering? These are interesting things to consider.
