Right - it unquestionably is a custom rule. But it's not as broad as it is made out, not is it the fundamental problem here. The Post Office knew the system is

Right - it unquestionably is a custom rule. But it's not as broad as it is made out, not is it the fundamental problem here. The Post Office knew the system is faulty, hid that evidence and lied in court under oath about it. As to lack of evidence... It's not so simple. A popular UK insurance hack is when people overtake you on a motorway and slam the brakes, to make a claim on your insurance. Unless you present evidence this was done to you, like dashcam footage, you are presumed to be responsible. You don't need the scammer to prove they didn't crash into you. I'm sure the US has similar mechanisms, where fault is presumed, like if a car hits a pedestrian. This is similar. Computer systems are presumed to be correct unless evidence is presented. Maybe it's a bad rule, but it's not the horrendous dystopian catastrophe it is declared to be everywhere.