Williams v. Illinois

Supreme Court of the United States · 2012 · Evidence

567 U.S. 50 (2012)

Updated August 1, 2026

Evidenceexpert basisconfrontationConfrontation ClauseCrawfordexpert opinionRule 703DNA evidence

Facts

At petitioner's bench trial for rape, Sandra Lambatos, a forensic specialist at the Illinois State Police lab, testified that a DNA profile produced by Cellmark, an outside accredited laboratory, matched a DNA profile the state lab produced from petitioner's blood. Lambatos explained business-record shipping manifests showing that vaginal swabs taken from the victim were sent to Cellmark and returned, but Cellmark's report itself was not admitted into evidence or shown to the factfinder. Lambatos did not testify about how Cellmark handled or tested the sample and did not vouch for the accuracy of Cellmark's profile. The defense objected on Confrontation Clause grounds to her testimony insofar as it implicated events at Cellmark, but the trial judge admitted the testimony and found petitioner guilty.

Issue

Whether the Confrontation Clause bars a prosecution expert from testifying that a DNA profile produced by an outside laboratory matched a profile produced from the defendant's blood when the outside laboratory's report was not admitted into evidence and the expert referred to the outside profile as coming from semen on the victim's vaginal swabs. Also, whether the outside laboratory's report would be testimonial if considered for its truth.

Rule

The Confrontation Clause does not apply to out-of-court statements that are not offered to prove the truth of the matter asserted, including statements related by an expert solely to explain the assumptions on which the expert's opinion rests. Independently, the Clause does not bar use of an out-of-court forensic statement whose primary purpose was not to accuse a targeted individual or create evidence against that person at trial, especially where the report was produced before any suspect was identified and the profile was not inherently inculpatory.

🔒

See the holding & full analysis

Create a free KwikCourt account to unlock the rest of this brief — and practice the case.

The court's holding and reasoning
Doctrine tests, pitfalls & exam hypotheticals
10 practice questions + 4 AI-graded essays on this case

Free sample · practice this case

Test yourself

One of 10 multiple-choice questions for this case. Pick an answer to see why.

In a bench trial in Milwaukee, Nora Paredes is prosecuted for armed sexual assault. The State calls Dr. Eli Mercer, a forensic DNA analyst at the state lab, who testifies that he compared a DNA profile generated by a private accredited laboratory from a crime-scene swab with a profile the state lab generated from Paredes's blood and found a match; the private lab's report is not admitted, and Mercer says he relied on that outside profile only in making his comparison.

Paredes argues that Mercer's testimony violated the Confrontation Clause because no analyst from the private laboratory testified. How should the court rule under the lead opinion?

Explanation. Under the lead opinion, the Confrontation Clause does not apply to out-of-court statements not offered for their truth. An expert may express an opinion based on facts made known to the expert, and in a bench trial the judge is presumed to understand the limited, non-truth use of basis evidence. Because the outside report itself was not admitted and the expert referred to it only as a premise for his own comparison, the Clause is not violated.