This is a tricky one, because you could just claim that the system wrote audit trails that show you did something due to a bug. How do you prove it either way?
In the case of the sub-postmasters the Post Office, as far as I'm aware, never proved where these stolen sums supposedly went. The computer evidence was thought terminating and was the only thing (except false confessions under duress) used to secure these convictions, rather than proper investigative work.
It's crazy auditors didn't spot discrepancies especially with the high base rate of reported frauds and errors, but if finding the receipts for stolen money was the threshold for prosecution any remotely competent thief would be in the clear
If there is absolutely nothing to corroborate the money going missing, no evidence presented for where or how the money was stolen then there shouldn't be enough to send someone to prison.
The amounts of money involved may be small to business owners in other domains but for SPMs many were almost bankrupted by trying to replace the sums out of their own earnings as you say. This wouldn't have been a rounding error to their lifestyle, it should have been provable to any halfway decent investigator. And if not? Then they get away with it and it's the price we pay not to live in tyranny.
Well, yeah. A defendant should be able to argue that because that can (and did) happen and it's bad to routinely wrongly convict people.
I thought when you called it a "tricky one" you were expressing that it might be a bad thing if it were difficult to convict someone based primarily on audit logs.
But if you don't want people to be wrongly convicted, then surely that's a good thing, right? As we know, there's no guarantee a particular audit log is correct.
Think of it like a diagnostic test, like covid tests. That sort of test has 2 measures, not one (anyone who just says "Test X is 95% accurate!" is selling you something) - specificity and sensitivity. Sensitivity is the percentage of true positives it generates out of all positives, and specificity is the percentage of true negatives it generates out of all negatives.
I don't want people to be wrongly convicted, no, so I want legal tests to have a very high specificity. But I could do that easily, by just throwing every case out as not guilty. The hard bit is raising sensitivity at the same time. You can't just say "if you don't want people to be wrongly convicted", because that justifies far too many things.
> As we know, there's no guarantee a particular audit log is correct.
There's no guarantee anything is correct. Three witnesses could have colluded and someone might go to jail for it, but unless there's a reason to think they colluded, we don't assume that. That's the problem I'm talking about: how do we get a feel for software systems without assuming like the Post Office that they work, or like you that they don't work?