## Facts

- A downtown New Orleans savings and loan was robbed on May 21, 1985, of about $2,640; surveillance photos and videotape captured the robber’s appearance.
- Three bank employees viewed the videotape and confirmed it depicted the robber; they later identified a still-photo enlargement as the robber.
- After copies of the surveillance images were circulated, an unidentified person suggested the robber resembled Dr. Victor Alexander, a physician with an office nearby.
- Agents presented the employees with a photo array including Alexander’s driver’s-license photo; each employee independently identified Alexander as the robber.
- At trial, the prosecution’s case linking Alexander to the robbery depended primarily on the surveillance images and the resulting eyewitness identifications.
- Alexander asserted mistaken identity and sought to present two defense experts: an orthodontist specializing in cephalometrics (scientific measurement of head/facial dimensions) and a former FBI photographic-comparison expert.
- Both experts reviewed the surveillance materials and were prepared to offer technical testimony that, in their view, the robber depicted could not be Alexander, including explanations of facial-measurement comparisons and photographic distortion effects.
- The district court excluded both experts, reasoning that jurors could compare the photographs to Alexander without expert assistance, and the jury convicted.

## Issues

1. Whether the district court abused its discretion under Federal Rule of Evidence 702 by excluding defense expert testimony on cephalometric and photographic-comparison analysis when identity was the central disputed issue.
2. Whether exclusion of that expert testimony improperly impaired the defendant’s ability to present a mistaken-identity defense and, if erroneous, whether the error was harmless.

## Decision

- The Fifth Circuit reversed the conviction and remanded for further proceedings.
- The court held the district court erred by excluding the defense experts on the premise that lay jurors were equally equipped to perform the underlying technical analysis.
- The court concluded the error was not harmless because the excluded testimony directly addressed the prosecution’s central identification evidence and was critical to the defense.

## Legal Principles

- Expert testimony is admissible under Federal Rule of Evidence 702 when specialized knowledge will assist the trier of fact in understanding evidence or determining a fact in issue.
- Technical testimony about measurable facial-dimension analysis (cephalometrics) and photographic distortion/pictorial comparison can exceed ordinary lay perception and may assist jurors evaluating identification evidence.
- A court may abuse its discretion by excluding qualified expert testimony that bears directly on a core disputed issue on the unsupported assumption that jurors can perform the same analysis unaided.
- When the prosecution’s case substantially rests on photographic evidence and related eyewitness identifications, erroneous exclusion of defense expert testimony undermining that identification may require reversal if it could have affected the verdict.

## Conclusion

The Fifth Circuit ordered a new trial because the district court improperly prevented the defense from presenting expert, technical evidence challenging photographic identification, and that exclusion was prejudicial given the prosecution’s reliance on surveillance images and eyewitness identifications derived from them.


United States v. Alexander, 816 F.2d 164 (5th Cir. 1987)