Under Rule 404(b), for what permissible purposes may evidence of other crimes or acts be admissible?

• A. Evidence of other crimes or acts may be admissible to prove motive, opportunity, intent, preparation, plan, knowledge, identity, or absence of mistake, if relevant and not unduly prejudicial.
• B. Evidence of other crimes or acts must always be excluded.
• C. Only the defendant's acts can be used for impeachment.
• D. It allows character evidence to prove propensity.

Answer: (B)

Rule 404(b) allows evidence of other crimes or acts to be admitted for purposes other than showing a person’s character or propensity. When the evidence is relevant to a material issue and its probative value is not substantially outweighed by unfair prejudice (the Rule 403 balancing), it may be introduced to prove things like motive, opportunity, intent, preparation, plan, knowledge, identity, or absence of mistake or accident. These uses focus on proving a fact about the current case (for example, that the defendant acted with intent or had a plan) rather than simply showing that the person is generally bad.

That’s why this option is correct: it lists the permissible purposes recognized under Rule 404(b) and includes the condition that the evidence must be relevant and not unduly prejudicial. The other choices are incorrect because this rule does not require exclusion in all cases; it does allow admission for these non-propensity purposes. It is not limited to the defendant’s acts, nor is it about admitting character evidence to prove propensity, which would run afoul of the general prohibition in Rule 404(a).