It's hard because (especially now) the second the accusation is made, the hammer is upon you - if not legally then definitely socially. Even if only 1% of accusations are false, that must be cold comfort for those few. That said, things are bad enough and you can't be discouraging survivors from coming forward, so there would have to be a pretty high standard to charge someone like that - not just identifying the wrong person, but knowing it's the wrong person, or just making up what happened entirely. In the latter case it's akin to perjury, so probably a similar sentence would be in order. And heaven help them if anything DOES happen with that on their record.