Reasonable just means there’s no good way to have a bright line rule and we have to consider these questions one at a time, in context.
The prosecutor has a vested interest in making you look like a bad person. Even if there is no evil in your heart, they will dig into your history and find some dirt, then lie and twist your words to make you into some sort of evil hacker, so that the "reasonable" people on your jury, seeing the prosecutor's version of you, is going to think you deserve prison time.
The use of "reasonable" in generally used to qualify some standard of behavior or conduct that is expected from individuals in specific situations. Because "reasonable" is inherently subjective, the responsibility for making the determination is (generally) passed over to a jury who will weigh what the prosecution and defense have presented which entails previous cases, the specific fact pattern of the case being deliberated, etc.
There are also situations where an actual judge makes the determination but generally, in a criminal context, it's up to a jury.
All that said, though, reasonableness standards exist all over the law and don’t all necessarily serve the same purpose or function exactly in the same way, when you get into the weeds.
Because if FAA tries to come up with a definition, there will always be weird unjust corner cases. Or just ban the paragliders whatsoever. I think the current ambiguity is the best compromise.
Judges typically consider matters of law. Usually “reasonable” is a cue that you are discussing a matter of fact, which is the province of the jury.
Sometimes you will have something called a bench trial, where it is agreed that the judge will also serve the role of the fact finder, and there will be no jury.
And then there are motions for a JMOL (see FRCP 50), where a judge has to decide whether a “reasonable jury” could have a legally sufficient basis to find in favor of a party.
Law as the verkehrte Welt of itself. :)
