About 30 years ago,I was done for drink-drive. No complaints; the court had limited powers, so any miscarriage was unlikely on a guilty plea. I think that was legal justice :)
I used to see it every Monday to Friday and only twice did I think the man should not have been convicted by the jury and there were no grounds for appeal. In both cases the judge was sympathetic, and the man didn't serve an extra day in jail. I always suspected that he thought the man was unlucky too.