> the defence legal team may be unsure how to persuade a jury (since they aren't IT experts) that this might not be so

Then they're a crap defense.

They find an expert witness -- an IT witness in this case -- for their side to explain how the software might make errors, how no software is perfect, etc. Having opposing expert witnesses, one for prosecution and one for defense, is standard.

Lawyers don't need to be domain experts in every, or even most, cases they take on. They do need to find experts though.