What I should also say is the rules about what can and can't be disclosed are more complicated than this allows. There are times when previous convictions etc can become discoverable but there have been recent changes to protect witnesses from having their lives thrown into chaos

In the case of Pensevie vs The State. This would be Lucy making her claim, Susan and Peter refuting it based on their honest testimony. And then Edmund getting up to support Lucy and having his detention record read out, followed by things the Nanny said about his behaviour, and then some confessions from Jonathan who Edmund kissed at boarding school - grotty little pervert. (it's the 1940s after all). In this case, the Edmunds of the world would never provide testimony. :o)