## Facts

- William A. Fensterer was convicted in Delaware state court of murdering his fiancée, Stephanie Ann Swift; the State alleged he strangled her with a cat leash.
- The prosecution introduced FBI hair-comparison testimony to link hairs found on the leash to Swift and to show one hair had been “forcibly removed.”
- FBI Special Agent Allen Robillard testified that one hair was forcibly removed and described three possible indicators (follicular tag, elongated/misshapen root, or skin sheath), but stated he could not recall which indicator he relied on in reaching his conclusion.
- On cross-examination, Robillard still could not identify his specific basis and clarified that “forcibly removed” could include minimal force, such as brushing hair.
- The trial court admitted the testimony over defense objection, ruling the inability to recall the basis affected weight, not admissibility.
- The defense cross-examined Robillard and presented its own expert, Dr. Peter DeForest, who agreed the hairs were similar to Swift’s, noted a follicular tag, and criticized the “forcible removal” inference.

## Issues

1. Whether admitting an expert opinion when the expert cannot recall the specific basis for the opinion violates the Sixth Amendment Confrontation Clause.
2. Whether due process is violated when the prosecution, knowing pretrial of the expert’s inability to recall the precise basis, still presents the opinion testimony.

## Decision

- The U.S. Supreme Court reversed the Delaware Supreme Court’s judgment.
- The Court held that admission of Robillard’s opinion did not violate the Confrontation Clause because the defense had a full opportunity to cross-examine him about his conclusion and his memory lapse.
- The Court held due process did not require the State to refrain from introducing the testimony merely because it knew the expert could not specify the precise basis for his opinion.
- The Court treated the expert’s inability to recall the basis as a matter for the jury’s evaluation of credibility and weight.

## Legal Principles

- The Confrontation Clause guarantees an opportunity for effective cross-examination, not cross-examination that achieves the defense’s preferred result.
- When a witness appears at trial and is subject to unrestricted cross-examination, the Confrontation Clause is generally satisfied even if the witness cannot remember details supporting the testimony.
- An expert’s inability to recall the specific basis for an opinion does not, by itself, make the opinion constitutionally inadmissible; the deficiency may be exposed to the factfinder through cross-examination and competing evidence.
- Prosecutorial foreknowledge of an expert’s memory limitations does not, without more, create a due process duty to withhold the expert’s testimony.

## Conclusion

The Court held that the Sixth Amendment was satisfied because the defense could cross-examine the State’s expert and present contrary expert evidence, and that due process did not bar the testimony despite the prosecution’s awareness of the expert’s inability to recall the opinion’s precise basis.


Delaware v. Fensterer, 474 U.S. 15 (1985)