Earlier quoted context omitted.
Your question makes a good point. Punishment is only effective at the bottom of the funnel. A well designed system, whether a computer or an organization should always have controls that guide things to where they should be. That means carrots and sticks. In a place like a post office, that means separation of duties, audit, and clear lines of accountability. Things fail when nobody asks awkward questions or looks. I…
In principle there was already some separation of duty as solictors in England owe a duty to the Court regardless of who pays them. However it seems not to have been enough in this case. Hopefully will be looked into.
The problem here was that as many sub-postmasters were co owned by a husband and wife with children. There was an enormous incentive for one of the sub post masters to plead guilty and say, "my wife had nothing to do with it." Doubly so as the sentences would often be on the cusp of the "suspendible range", a guilty plea combined with contrition is much more likely to get a judge to suspend your sentence if he can.
Of course, this "plea-bargaining" is standard practice in the states but we aren't used to it in the UK.
The issue is that no barrister would allow their client to plead guilty without giving them a little canned speech about not pleading guilty if they didn't do it and having them, "sign their brief".