> In Commonwealth countries, it's possible to initiate a private prosecution (by a person who hasn't received criminal justice). These don't usually get very far

This is what happens when they do: https://en.wikipedia.org/wiki/British_Post_Office_scandal

> Between 1999 and 2015, more than 900 subpostmasters were wrongfully convicted of theft, fraud and false accounting based on faulty Horizon data, with about 700 of these prosecutions carried out by the Post Office. Other subpostmasters were prosecuted but not convicted, forced to cover illusory shortfalls caused by Horizon with their own money, or had their contracts terminated. The court cases, criminal convictions, imprisonments, loss of livelihoods and homes, debts, and bankruptcies led to stress, illness and family breakdowns, and were linked to at least thirteen suicides.

Hundreds of innocent people went to prison, were financially ruined, thirteen took their own life, because a well-funded entity found it easier to privately prosecute its contractors than to question its software vendor. And the court system let them do it.