I'm asking genuinely, how do you know you are defending a clean ship?
Do you look at the fight going on and assume that ship 1 is the good guy and ship 2 is the bad guy? Do you scan one of the ships randomly, see they are clean, assume then that the other ship is a wanted criminal and open fire?
Pretty much.
Often you can see laser-fire in the distance and you can't target all of the combatants.
If you target one and they're clean it's a reasonable assumption that the ship(s) that ship is attacking are wanted.
After all, if the ship you targeted had shot first, that'd be the wanted ship.
Bearing in mind that it's often DBS's that attack, in packs, in RES's, you often have to get closer than 1km before you can target them so the only option is to try and score a hit on them without targeting them in order to try and divert their attention from their target.
Why is it so challenging in either of those situations to wait the 4 seconds to complete the scan on the presumed wanted ship to determine its status?
As above, when you've got 3 or 4 ships all attacking a clean ship and you're 2km away, by the time you've closed the distance so you're close enough to scan them all, target them and shoot them in order to distract them from their target, you can be looking at 30 seconds or more and that's certainly plenty of time for an innocent ship to be destroyed.
Obviously you are taking a risk by pre-emptively attacking another ship but that's a choice the player should be free to make.
It's daft that a ship might be in the middle of committing a criminal attack and still report another ship for engaging them without scanning first.
Fundamentally, the scan shouldn't have anything to do with whether or not you are considered to have committed a crime.
Attack a clean ship and you've committed a crime.
Attack a wanted ship and you haven't.
Simples!