What Is 404(b) Evidence And When Is It Admissible?

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404(b) evidence is evidence of prior bad acts that the prosecution can introduce in their case-in-chief. Under Federal Rule of Evidence (commonly abbreviated ‘FRE’) 404(b), the prosecution is able to introduce evidence of Defendant’s prior bad acts that are not charged in the instant criminal case. Although introduction of 404(b) evidence is not permissible to show the individual’s criminal propensity, or pre-disposition to commit crimes, FRE 404(b) is admissible for other reasons.

When Is FRE 404(b) Evidence Admissible?

Federal Rule of Evidence 404(b) provides that prior act evidence “is not admissible to prove the character of a person in order to show action in conformity therewith,” but it is admissible for several other purposes. Specifically, FRE 404(b) evidence can be admissible for purposes such as proof of:

  • Motive,
  • Opportunity,
  • Intent,
  • Preparation,
  • Plan,
  • Knowledge,
  • Identity, OR
  • Absence of mistake or accident.

Is FRE 404(b) Evidence Admissible in Federal Court or in State Court?

FRE 404(b) evidence is admissible in federal cases. However, New York State has a similar provision, however under a different name. Under a criminal case from 1901, titled People of the State of New York, the prosecution is able to make what’s called a Molineux application. In its purpose, it is identical to FRE 404(b). However, the difference is that FRE 404(b) comes from a statute, while New York’s Molineux application comes from a judicial opinion on a criminal case.

When is FRE 404(b) Application Made?

The prosecutor will make a FRE 404(b) application as a motion in limine before trial. The reason why a 404(b) application is made before trial is to give both sides an opportunity to present their arguments to the judge as to whether this FRE 404(b) evidence should be presented at trial.

What is the Standard for Admitting FRE 404(b) Evidence?

Whether to admit FRE 404(b) evidence is within the discretion of the trial judge. In order to decideThere is a four-factor test that the Court must consider in determining whether FRE 404(b) evidence is admissible at trial. These are called the Huddleston factors, from a 1988 Supreme Court case called United States v. Huddleston. To determine whether evidence if uncharged crimes is admissible at trial, the Court must consider whether:

  1. Evidence of uncharged crime(s) was offered for a proper purpose, AND
  2. It was relevant to a disputed trial issue, AND
  3. Its probative value is substantially outweighed by its possible prejudice; AND
  4. The Trial Court administered an appropriate limiting instruction.

In the Second Circuit (federal courts for New York, Connecticut and Vermont), the Courts have an “inclusionary” approach to FRE 404(b) evidence. That is to say, that FRE 404(b) evidence should generally be included, unless there is an issue with the Huddleston factors.

What is the a Limiting Instruction?

A limiting instruction is a jury instruction that the judge reads as part of the jury charge – after summations, but before deliberation, that explains that the 404(b) evidence that was presented by the prosecutor was presented for a limited purpose. Namely to explain Motive, Opportunity, Intent, Preparation, Plan, Knowledge, Identity, or Absence of mistake or accident.

The Jury will also be told that they are not allowed to consider FRE 404(b) evidence as proof of Defendant’s criminal propensity. That is to say that just because the prosecutor presented evidence of the Defendant committing prior bad acts that are not charged in the instant indictment, the jury is not allowed to use those prior bad acts as proof that the Defendant committed the crimes charged in the indictment.

When Can FRE 404(b) Evidence Be Excluded?

If the Court determines that the four Huddleston Factors are not met, the Court will exclude FRE 404(b) evidence. Frequently, it is the third Huddleston Factor that results in FRE 404(b) evidence not being admissible. Specifically, in determining whether to admit FRE 404(b) evidence, the Court must look at whether the probative value of the evidence is substantially outweighed by a danger of unfair prejudice,

Additionally, the Court may exclude relevant evidence if its probative value is substantially outweighed by a danger of one or more of the following:

  • Confusing the issues,
  • Misleading the jury,
  • Undue delay,
  • Wasting time, OR
  • Needlessly presenting cumulative evidence.

These factors are enumerated in Federal Rules of Evidence 403.

What is Danger of Unfair Prejudice for FRE 404(b) Evidence?

The Courts have explained that in criminal cases, the term “unfair prejudice” speaks to the capacity of some concededly relevant evidence to lure the factfinder into declaring guilt on a ground different from proof specific to the offense charged.” 


If you have questions regarding the admissibility of FRE 404(b) evidence in a federal case or Molineux evidence in a New York State case, please contact us to schedule your initial consultation. We have litigated numerous FRE 404(b) motions in federal court and Molineux applications in New York State Court.