## Facts

- Terry Lee Shannon was prosecuted in federal district court and raised an insanity defense under the Insanity Defense Reform Act of 1984 (IDRA), 18 U.S.C. §§ 17, 4241–4247.
- Shannon requested a jury instruction explaining that a verdict of “not guilty only by reason of insanity” (NGI) would result in involuntary commitment rather than immediate release.
- The district court refused to give the requested instruction, and the jury returned a guilty verdict.
- The Fifth Circuit affirmed, applying the general federal rule that juries should not be informed of the consequences of their verdicts.
- The Supreme Court granted certiorari to determine whether the IDRA or federal practice required the requested instruction.

## Issues

1. Whether, in a federal criminal trial under the IDRA, the court must instruct the jury about the post-verdict consequences of an NGI verdict, including involuntary commitment.
2. Whether the IDRA implicitly incorporated a requirement for such instructions by creating a special NGI verdict and a federal commitment scheme.
3. Whether, apart from the IDRA, general federal practice requires an NGI-consequences instruction to prevent juror misunderstanding.

## Decision

- The Supreme Court affirmed the judgment, holding that a federal district court is not required to instruct the jury on the consequences of an NGI verdict.
- The Court held that neither the IDRA’s text nor general federal practice mandates informing jurors about post-verdict disposition following an NGI verdict.
- The Court reasoned that juries are assigned factfinding, while sentencing and related consequences are assigned to the judge; consequence instructions risk confusing jurors and distracting from evidence-based deliberation.
- The Court rejected reliance on legislative history and analogies to District of Columbia practice as insufficient to create an instruction requirement absent statutory text.
- The Court recognized a limited, case-specific possibility of a curative instruction when necessary to correct a clearly misleading impression created during trial, but treated that as discretionary rather than mandatory.

## Legal Principles

- In federal criminal trials, juries generally should decide guilt or innocence based on the evidence and the court’s legal instructions, not on the consequences of a verdict.
- The IDRA does not require an instruction informing the jury that an NGI verdict leads to involuntary commitment under federal commitment procedures.
- Legislative history cannot supply an instruction requirement that is not supported by statutory text.
- A trial court may, in exceptional circumstances, give a limited curative instruction to correct a specific false or misleading suggestion about the defendant’s post-verdict status, but there is no general entitlement to an NGI-consequences instruction.

## Conclusion

The Court held that federal trial courts need not instruct juries on the involuntary-commitment consequences of an NGI verdict under the IDRA, reaffirming the general rule that jurors should not consider verdict consequences, while leaving narrow discretion for curative instructions in unusual cases involving trial-created misimpressions.


Shannon v. United States, 512 U.S. 573 (1994)