United States v. Ewell

Carlton Ewell (defendant) moved to suppress DNA evidence that the government (plaintiff) planned to present at Ewell’s federal criminal trial. At a pretrial hearing, the government presented expert witness Dr. Bruce Budowle, a senior scientist at the Federal Bureau of Investigation (FBI) laboratory, which performed PCR/STR typing in Ewell’s case. PCR/STR typing proceeded in two steps: First, scientists used the polymerase chain reaction (PCR) technique to amplify (or copy) short segments of DNA millions of times to prepare a DNA sample. Second, scientists looked for short tandem repeats (STRs), a feature in DNA sequences that could help scientists narrow down a full DNA sequence to focus on just 13 loci (or allele sites) that meaningfully varied from person to person. Budowle testified that although PCR/STR typing was relatively new, PCR amplification was widely accepted, and PCR/STR typing was materially similar to other DNA-typing methods that scientists had accepted as reliable. The government presented evidence of many validation studies of PCR/STR typing. The FBI laboratory’s detailed protocol and auditing process complied with current industry standards to maintain quality control in every stage of PCR/STR typing. Budowle opined that if a forensic DNA analyst followed the FBI protocol and used properly calibrated instruments, the error rate of PCR/STR typing was essentially zero. Ewell’s expert witness, Dr. Theodore Kessis, countered that the error rate was likely one in 200. The district court ruled that the DNA evidence generated through PCR/STR typing was admissible at Ewell’s trial. Ewell later moved for a new trial, arguing that the PCR/STR typing evidence admitted at Ewell’s trial failed to meet the Daubert standard because (1) scientists had not proven the reliability of the mass-manufactured chemical kits used to process Ewell’s DNA, (2) peer review of PCR/STR typing may have been biased because many forensic DNA analysts had ties to the FBI, (3) the government had failed to present evidence about how often the FBI laboratory actually committed errors in PCR/STR typing, and (4) the FBI protocol was inadequate under the industry’s initial standards.