Earlier quoted context omitted.
The actual answer to this is terrible. Courts had to trust the computer was correct. There was a common law presumption that a computer was operating correctly unless there is evidence to the contrary (and getting that evidence is basically impossible for the individuals being charged who were post office workers, not computer experts, and the source code was a trade secret). This might change, partly in response to…
> The actual answer to this is terrible. Courts had to trust the computer was correct. There was a common law presumption that a computer was operating correctly unless there is evidence to the contrary That is just mind bogglingly stupid - who the hell are the idiots who wrote a law like that? Any of them wrote a line of code in their life?
Imagine a witness says "I saw him go into the bank at 11:20. I know the time because I looked up at the clock tower, and it said 11:20".
Defence argues "The clock must have been wrong. My client was at lunch with his wife by 11:15".
Clocks are simple enough that we can presume them to correct, unless you can present evidence that they are unreliable.
This presumption was extended to ever-more complicated machines over the years. And then (fatally) this presumption was extended to the rise of PROGRAMMABLE computers. It is the programmability of computers that makes them unreliable. The actual computer hardware rarely makes an error that isn't obvious as an error.
The distinction of software and hardware is a relatively recent concept for something as old as common law.