That's a bit of a red herring - in the cases we have been discussing on this thread there aren't eye witnesses but victims.  It's hardly likely that in the case of someone they knew they would be mistaken in identifying their attacker or being mistaken about what was done to them!

A single accusation on its own with no other supporting evidence is unlikely to be relied on to secure a conviction - that doesn't mean to say that anyone making such an accusation should be treated on a basis of disbelief - that is how it used to be and what prevented many of these cases from being dealt with at the time.  

Thankfully we treat current cases far more seriously and with an open mind.

I've been trying to think of any reports I've seen where an accused who has been acquitted in one of these cases has taken civil action against multiple accusers - the standard of proof is much lower in a civil case.