## Facts

- William Wayne Macumber was charged in Arizona with two counts of first-degree murder arising from a double homicide in the desert near Scottsdale.
- At trial, the State relied heavily on firearms-identification evidence based on spent .45-caliber shell casings recovered from the scene.
- A State witness from the FBI Firearms Identification Unit testified that distinctive ejector-mark characteristics meant the casings could only have been fired from a particular .45-caliber semiautomatic pistol linked to Macumber.
- The defense sought to call Charles M. Byers to dispute the State’s firearms-identification conclusions. Byers had a degree in chemistry, had studied firearms identification, had worked for weapons manufacturers, and had written articles in the field.
- Byers examined the pistol and the casings and reached a conclusion contrary to the FBI witness, but the trial court refused to qualify him and excluded his testimony in full.
- Separately, two attorneys (who were not Macumber’s counsel) had previously represented another man who later told them that he had committed the murders for which Macumber was being prosecuted.
- That former client later died. After learning Macumber had been charged, the attorneys sought guidance and received an informal ethics opinion from the state bar ethics committee indicating the attorney-client privilege did not prevent disclosure to the defense, prosecution, and court.
- The attorneys were willing to testify at Macumber’s trial about the confession, but the trial court ruled the confession remained protected by attorney-client privilege and barred their testimony.
- A jury found Macumber guilty on both counts, and the court imposed two concurrent life sentences.
- Macumber appealed, challenging (among other things) the exclusion of Byers and the exclusion of the attorneys’ confession testimony.

## Issues

1. Did the trial court abuse its discretion by refusing to qualify the defense firearms-identification witness and excluding his testimony, where the testimony would directly contradict the State’s central ballistics evidence?
2. Did the trial court err by applying attorney-client privilege to bar two lawyers from testifying that their now-deceased former client confessed to the murders for which Macumber was on trial?

## Decision

- The Arizona Supreme Court reversed Macumber’s convictions and remanded for a new trial.
- The court held the trial judge erred in excluding Byers’s firearms-identification testimony; his level of training and study was sufficient to assist the jury, and any limits in his background affected weight rather than admissibility.
- The court also held the confession evidence was wrongly excluded on privilege grounds under the circumstances presented, and that excluding it contributed to the need for a new trial.

## Legal Principles

- A trial judge has discretion to determine whether a witness may testify as an expert, but that discretion is subject to review for legal error.
- An expert is someone whose opinion rests on special knowledge beyond that of ordinary jurors and can help the jury understand the evidence; the witness need not have the highest degree of skill or the most extensive credentials.
- Limits in an expert’s background, including lack of prior work in a narrow sub-area of a field, ordinarily go to the weight of the testimony and are tested through cross-examination and competing proof, not wholesale exclusion.
- Attorney-client privilege is strong and generally survives the client’s death, but it is not applied mechanically where doing so would block highly exculpatory evidence and risk convicting the wrong person.
- When proffered evidence consists of a deceased client’s confession to the very crimes for which another person is on trial, the court must account for the defendant’s ability to present a defense when deciding whether the privilege bars the testimony.

## Conclusion

State v. Macumber held that the trial court’s exclusion of both (1) the defense firearms-identification witness who would have contradicted the State’s ejector-mark testimony and (2) lawyers’ testimony about a deceased former client’s confession required reversal, because the jury was kept from hearing evidence bearing directly on whether Macumber was the shooter, so the convictions were reversed and the case was remanded for a new trial.


State v. Macumber, 544 P.2d 1084 (1976)