I'd guess a lot of those decisions are probably fairly insensitive to small changes in the risk. But if, say, the sentence duration for murder was gradually red

I'd guess a lot of those decisions are probably fairly insensitive to small changes in the risk. But if, say, the sentence duration for murder was gradually reduced towards 0 years, there'd have to be some kind of increase in offending. Maybe not linear, but at some point, people are going to be angry enough at their enemies to take the 1 year jail when they wouldn't take the 30 years. But for drink driving, you typically do it many times without getting caught, so you could respond to changed risk by changing how often you do it.