As noted above, it is a common misconception that FRE 404(b) applies only to criminal acts in criminal cases. FRE 404(b) applies to all prior acts, in any type of case, unless another rule or statute supplants the 404(b) analysis.
There is some dispute in the case law about the proper application of FRE 404(b) to prior act evidence in sexual assault and child molestation cases. Procedure: Rule 404(b) requires that, upon the request of the accused, the prosecution must provide reasonable pretrial notice of any “prior bad act” evidence that it intends to introduce at trial.