## Facts

- Clyde Mattox was indicted in federal court for the murder of John Mullen in the Indian Territory attached to the District of Kansas for judicial purposes.
- At trial, the prosecution introduced statements made by the victim while wounded to an attending physician.
- The defense sought to introduce an additional statement the victim allegedly made to Mattox’s mother exculpating Mattox, offered as a dying declaration.
- The trial court excluded the exculpatory statement on the ground that the foundation for a dying declaration was not shown.
- After the jury retired to deliberate, a newspaper article unfavorable to Mattox was brought into the jury room and read before the verdict was reached.
- Mattox moved for a new trial and offered juror affidavits describing the reading of the article; the trial court excluded the affidavits as inadmissible and denied the motion.
- Mattox was convicted and sentenced to death; he sought review by writ of error.

## Issues

1. Whether the trial court erred by excluding the defense’s proffered exculpatory statement as a dying declaration without a sufficient showing that the declarant believed death was imminent when it was made.
2. Whether juror affidavits were admissible to prove that the jury was exposed during deliberations to a prejudicial newspaper article, and whether excluding those affidavits required reversal.

## Decision

- The Supreme Court held that exclusion of the alleged exculpatory dying declaration was not error because the defense failed to establish that the declarant spoke under a settled belief of impending death at the time of the statement.
- The Court held that the trial court erred in excluding juror affidavits offered to prove that an extraneous, prejudicial newspaper article was read in the jury room during deliberations.
- The Court reversed the conviction and remanded for a new trial based on the juror-exposure issue.

## Legal Principles

- A ruling that categorically excludes affidavits supporting a new-trial motion presents a reviewable legal question on writ of error when the trial court does not exercise discretionary weighing but instead treats the evidence as inadmissible as a matter of law.
- Dying declarations are admissible in a murder trial on the identity of the killer and circumstances of the homicide for the defendant as well as the prosecution, but only if the proponent shows the declarant believed death was imminent when the statement was made.
- Juror testimony may not be used to prove internal deliberative processes (mental impressions, motives, or how evidence affected jurors).
- Juror testimony is admissible to prove external events and extraneous influences (overt acts) affecting the jury, including the introduction of outside information such as prejudicial media during deliberations.
- Exposure of a deliberating jury to private, potentially prejudicial external communications or materials is forbidden and can require a new trial unless harmlessness is shown.

## Conclusion

The Court affirmed the evidentiary exclusion of an asserted exculpatory dying declaration for lack of proof that the declarant spoke under an imminent-death belief, but reversed because the trial court improperly refused to consider juror affidavits establishing that the jury was exposed during deliberations to prejudicial extraneous material.


Mattox v. United States, 146 U.S. 140 (1892)