Arbitrary and Capricious, Eighteenth-Century Style

I'm doing some reading for my British History class about the criminal "justice" system in England in the 1700s. Apparently, during that century Parliament passed an awful lot of new laws authorizing capital punishment for various offenses against property. However, the number of actual executions for crimes against property didn't increase much at all, even as the number of convictions for capital crimes against property did. Why? Because an awful lot of death sentences got commuted by royal prerogative into exile to, say, Australia. This happened on the recommendation of judges, and apparently the very same MPs passing the death penalty statutes were often the ones intervening to secure clemency. This seems like a bit of a puzzle, at first, but given the discussion of capital punishment in the contemporary era, and particularly my grandfather's book on the subject, there's a pretty obvious answer that occurs to me. When you have a lot of people getting convicted of capital crimes, most of whom don't actually get executed, it gives the people deciding to whom the pardons will be doled out a tremendous amount of arbitrary and capricious power. It's sort of analogous to what happens if you create a legal code in which just about everyone will be guilty of some minor offense, jaywalking, say, or something perhaps slightly less minor but equally routine, but where as a rule no one is prosecuted. That gives the authorities the ability to selectively enforce those laws against people they don't like, for one reason or another: political enemies, say, or more serious criminals they can't get on the main charges of murder, theft, whatever. And if you just look at the convictions, or in the 18th-century Britain case if you just look at the executions, you won't see anything wrong with the procedure: the people in question were guilty under law of committing crimes, and were punished accordingly. You only notice a problem when you see all of the people equally guilty not being punished, and start to wonder why some got away with their crimes while some had the book thrown at them.