Mattox v. United States (1892)

Supreme Court of the United States · 1892 · Evidence

146 U.S. 140 (1892)

Updated August 22, 2026

Evidencejuror impeachment of verdictextraneous influenceovert actsmental processes of jurorsbailiff communicationnewspaper read to juryharmlessness of outside contact

Facts

During jury deliberations in a capital case, the officer in charge told jurors that this was the third person Clyde Mattox had killed, and a newspaper article was read to the jury stating that Mattox had previously been tried for his life, that the evidence against him was very strong, that his friends had given up hope, and that a quick conviction was expected. Juror affidavits were offered not to describe the effect of these events on their minds, but to establish that the communications and reading occurred. Separately, the prosecution introduced testimony that the dying victim, after being told by the physician that he had no chance of recovery, said he did not know who shot him. Defense counsel then tried to ask whether the victim also said he knew Clyde Mattox and that Clyde was not one of the shooters, but the court excluded that question on incompetency grounds.

Issue

May juror affidavits be admitted to show outside influences or overt acts affecting the jury, even though jurors may not testify about the effect of those matters on their minds? Also, when a dying declaration is admitted, may the defendant elicit an additional connected statement made at the same time if the circumstances show the declarant spoke under a sense of impending death?

Rule

On a motion for new trial, juror testimony is inadmissible as to motives, mental processes, or the effect of influences on deliberations, but it is admissible to prove extraneous influences or overt acts open to the knowledge of the jury and not essentially inhering in the verdict. Private communications or outside materials reaching jurors are absolutely forbidden and invalidate the verdict unless their harmlessness is made to appear. Dying declarations are admissible for either side in a murder trial if the declarant spoke under a sense of impending death, shown by the declarant's words, the nature of the wounds, surrounding conduct, or communications from medical advisers assented to or understood by the declarant; and if part of such a statement is admitted, the opposing party may properly elicit the remainder of the connected declaration.

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In a homicide trial in Tulsa, juror Nina Flores submitted an affidavit after the verdict stating that during deliberations the courthouse janitor opened the jury-room door and said, "Everyone downtown knows Devin Cross has done this before." Nina's affidavit says only that the statement was made and heard by the jurors, not how anyone reacted to it.

On the defendant's motion for a new trial, is Nina's affidavit admissible?

Explanation. A juror may testify to overt external acts or extraneous influences reaching the jury, but not to the effect of those matters on deliberations or the jurors' thoughts. The affidavit is admissible because it is offered only to prove that an outside communication occurred. The rule does not require the juror to say the communication changed her mind; inquiry into mental effect is barred.