What's the difference between 1 and 2? Is 1 a good conditional?
I can't imagine the consequences if the police found out.
I couldn't imagine the consequences if the police found out.
I'd appreciate your help.
These are very tricky conditionals, because consequences is itself a proposition which 'hides' a middle term. I've put it in boldface:
I can't imagine the consequences if the police found out.
In the hypothetical case of the police finding out, there would be consequences; right now, in the real present, I am unable to predict those consequences. OR
(This could also be understood as In the as yet undetermined case that the police did find out, there { were / will be } consequences; right now, in the real present, I am unable to say what those consequences {were / are / will be}.)
I couldn't imagine the consequences if the police found out.
In the hypothetical case of the police finding out, there would be consequences; at that time, in the hypothetical future, I would be unable to predict those consequences.
In both of these the middle term contains the modally remote (would) term which satisifes the requirement that the protasis (IF-clause) and apodosis (THEN-clause) must have the same modality. They are quite different from ordinary conditionals, with no middle term:
None of 1-4 is necessarily counterfactual; they will all support adding —and they will or —but they won't at the end. 5, if it bears the indicated construction cannot be understood as a counterfactual.
They're both right but they mean different things.
In your first sentence, you currently, while speaking, cannot imagine the consequences. "Can't" is thus the normal indicative mood.
In the second sentence, you're talking about a potential inability to understand in a hypothetical situation in which the police find out, and "couldn't" is conditional.
"I can't imagine the consequences if the police found out." - May be overlooked in the informal conversations or acceptable as speakers who aren't particularly conscious of their language or style speak this way.
On the other hand, "I can't imagine ... if the police find out." is correct and it's more like saying the same 'as a matter of fact' as if it's going to happen and it's only a matter of time.
The second follows the rules for such conditional sentences and puts forward a real hypothesis / assumption.