In a sexual assault case, the victim is on the stand.
In the past the victim has accused 5 different men of rape and all have been acquitted.
Defense wants to ask her on cross about those accusations for the purposes of showing that she is untruthful.
I'm assuming 412 would bar an inquiry into the specific instances surrounding the individual accusations, but an inquiry into the existence of the accusations and acquittals would seem to have 608(b) issues.
Because it is cross examination, the defense should be allowed to ask about those instances, yes?
However if she testifies that she did not falsely accuse 5 people, is the defense stuck with that answer? Can they ask another witness about the accusations? Can they introduce the charging document? If she sued these men in civil court, can those pleadings be introduced?
It would seem that the victim/accuser's truthfulness is a non collateral issue.
A lot to unpack here.
First, this evidence is not barred by 412, because prior false accusations of sexual assault are neither "other sexual behavior" nor "sexual predisposition" under 412(a).
If you are trying to use the prior accusations for substantive purposes (to show that the current allegations are also false and that the defendant is innocent), they are "other acts" for which you have to get past FRE 404(b). You cannot use them to show she is lying--that is action-in-accordance--so you look for a permitted 404(b)(2) use. The acquittals make be sufficient to support a finding that the prior accusations were false.
Alternatively, you can use these as specific instances of untruthful conduct on CREX under FRE 608(b) (the court can decide they were lies, since the defendants were acquitted). But if the victim denies the false accusations, you are stuck. Because character for truthfulness remains collateral.
To your last point: Character for truthfulness is always collateral. Even when it is the complaining witness in a criminal case.