Federal Rules of Evidence - Rule 404. Character Evidence Not Admissible To Prove Conduct; Exceptions; Other Crimes
(a) Character Evidence Generally.--Evidence of a person's character or a trait of character is not admissible for the purpose of proving action in conformity therewith on a particular occasion, except:
(1) Character of Accused.--Evidence of a pertinent trait of character offered by an accused, or by the prosecution to rebut the same, or if evidence of a trait of character of the alleged victim of the crime is offered by an accused and admitted under Rule 404(a)(2), evidence of the same trait of character of the accused offered by the prosecution;
(2) Character of Alleged Victim.--Evidence of a pertinent trait of character of the alleged victim of the crime offered by an accused, or by the prosecution to rebut the same, or evidence of a character trait of peacefulness of the alleged victim offered by the prosecution in a homicide case to rebut evidence that the alleged victim was the first aggressor;
(3) Character of Witness.--Evidence of the character of a witness, as provided in rules 607, 608, and 609.
(b) Other Crimes, Wrongs, or Acts.--Evidence of other crimes, wrongs, or acts is not admissible to prove the character of a person in order to show action in conformity therewith. It may, however, be admissible for other purposes, such as proof of motive, opportunity, intent, preparation, plan, knowledge, identity, or absence of mistake or accident, provided that upon request by the accused, the prosecution in a criminal case shall provide reasonable notice in advance of trial, or during trial if the court excuses pretrial notice on good cause shown, of the general nature of any such evidence it intends to introduce at trial.