Entered into Evidence

A phrenological map of the brain

Phrenological maps such as this one from the 1830s once played an important role in criminal investigations

Second, even as public fascination with and confidence in the use of forensic science in criminal investigation grows, many scholars and some judges question the reliability of fingerprint, hair, handwriting, ballistics, shoe-print, tire-mark, lip-print, tool-mark, voiceprint, and bite-mark analyses for identification, as well as polygraph tests and reports from unaccredited laboratories. While criminal forensic scientists frequently claim that the evidence they generate is nearly infallible, these claims have not been subjected to rigorous research to determine error rates. Moreover, several recent independent studies have revealed serious shortcomings on the part of handwriting, hair, and fingerprint identification analysts. Criticism of forensic expertise in criminal law is not new; over the last century the use of hypnosis, phrenology, and truth serum were each discredited and replaced by more modern forensic techniques. The recent spate of criticism, however, is a wholesale challenge to a wide range of techniques that have not been independently tested for reliability and potential errors.

Third, and most important, DNA profiling has become the “gold standard” for forensic evidence, and it has tended to eclipse all other identification techniques as erroneous and misleading. (Indeed, the potential for cytokine testing, a DNA technology to determine whether exposure to such chemical substances as benzene caused a claimed injury, is now being explored in the context of toxic tort litigation in civil courts.) Despite its close association with law enforcement laboratories, DNA profiling is rarely challenged successfully because of its scientific origins outside of legal contexts. Significantly, early DNA identification techniques, advertised by private firms as flawless and infallible, proved in retrospect to be unreliable. Criminal defense attorneys should be credited with raising the concerns that resulted in important improvement in DNA identification technologies.

A new concern, however, is on the horizon, and it may be instructive for recent challenges to the traditional forms of forensic evidence. The Innocence Project, through which hundreds of prisoners convicted of crimes (often on the basis of unreliable forensic evidence) have now proved their innocence through DNA testing, creates a strange alliance between prosecutors and defense counsel, who all now seem to agree that DNA profiling is flawless and infallible. There are not enough skeptics questioning the Federal Bureau of Investigation’s control of standards for DNA analysis, highlighting the potential role of interpretation and sampling errors, or demanding blind proficiency testing for DNA crime laboratories.

Contemporary criticism of science-for-litigation is oversimplified. To assume that DNA profiling is reliable because of its origins outside the courtroom, and that traditional criminal forensic evidence is unreliable because it originates in crime labs is to overlook both the potential errors in handling DNA and the reliability of numerous crime-lab techniques such as chemical analysis. Likewise, in the context of toxic tort litigation, to assume that industry studies are unbiased because they were performed prior to litigation and that studies performed after a lawsuit is filed are biased is to overlook both the potential interests of industrial laboratories and the scientific integrity of many expert reports prepared for trial. This assessment is neither a critique of DNA science nor an attack on industry science. Rather, it is a critique of the oversimplified notion that science outside the courtroom is disinterested and reliable, while science-for-litigation is interested and therefore unreliable. Both types of science are potentially methodologically sound, and both types of science are potentially biased. The proper distinction, therefore, is not between studies prior to and after litigation but between reliable studies, which may not be wholly disinterested, and unreliable studies, which may have been performed before or after litigation begins.

Rhetorical advocacy and institutional support are not the opposite of science but part of the context in which science progresses and succeeds. Efforts to improve forensic science in the criminal context are laudable, but the goal must be reliability, from any source, and not “disinterested science”; interests might, but do not always, signal unreliability.

David S. Caudill is CHF’s 2007/2008 Societé de Chimie Industrielle (American Section) Fellow and is a professor and the Arthur M. Goldberg Family Chair in Law at the Villanova University School of Law.