Pseudoscience and Forensics

For over a century, science has held out the hope that the administration of criminal justice can be placed on a firmer and more rational footing, one that does not have to rely on ambiguous circumstantial evidence or potentially unreliable eyewitness testimony to put criminals behind bars. Defendants may lie, and witnesses are often mistaken about what they know or have seen, but science relies on observable and testable facts. A criminal usually leaves behind physical evidence that can be found, examined, and identified through scientific techniques, and linked to the criminal in a way that gives new meaning to the phrase "beyond a reasonable doubt."

In the twentieth century, science began to take on an almost mystical aura of infallibility as some of the tools of the forensic trade began to emerge. The first case that relied on fingerprint analysis, for example, was heard in 1911 in Illinois (People v. Jennings ), and soon the claim that no two persons have identical fingerprints became axiomatic (taken for granted). In 1936, Bruno Richard Hauptmann was convicted for kidnapping and murdering the infant son of Charles Lindbergh, Jr., the first criminal of note to be executed largely on the basis of handwriting analysis . In 1979, the profile of forensic odontologists was boosted when bite mark testimony was allowed in the trial of serial killer Ted Bundy. In 1990, testimony about DNA , with its seemingly incontrovertible statistical claims about DNA matches, was admitted into evidence for the first time. Judges, juries, and members of the public accepted the testimony of forensic scientists with little question.

Skeptics, however, have demanded proof—in the form of clinical trials, publication, peer review, and measurement of error rates—that what forensic experts practiced was science and not pseudoscience. In the early years of the twentieth century, these skeptics performed a valuable service. They exposed the pseudoscientific claims of phrenologists, who asserted that the shape of the skull was indicative of mental faculties and character, so that criminal tendencies could be measured with a pair of calipers. Similarly, early handwriting analysts had little in the way of science to back their claims, and their analysis often shaded off into graphology, a pseudoscience that attempts to assess personality through unique handwriting characteristics. In the 1920s, toolmark examination was all the rage; in a rape trial, one examiner testified with apparent breathtaking scientific accuracy that to find an exact match of the knife blade used in the crime, "every one of the hundred million people in the United States" would have to have "six hundred and fifty quadrillion knives each." In the 1930s, efforts were made to link criminal tendencies with particular blood types, but the claims were abandoned when they were rejected by the scientific community as pseudoscience.

The skepticism that scuttled these pseudosciences was given renewed life in the aftermath of Daubert v. Merrell Dow Pharmaceuticals, a 1993 U.S. Supreme Court case that interpreted the 1975 Federal Rules of Evidence as they pertained to the admissibility of expert testimony, including that of forensic scientists. Under the so-called Daubert standard, judges were required to act as gatekeepers for scientific testimony and to demand that the testimony of forensic scientists (and other experts) has a valid, reliable, and relevant foundation.

Arson investigators, for example, have long searched for signs of chipped concrete at fire scenes. Their assumption is that an accelerant such as gasoline causes concrete to "fragment," but laboratory tests have called this assumption into question, casting doubt on the validity of this mainstay of arson investigation science. Similarly, many defendants have been convicted of crimes based on visual comparisons of hair fibers . However, 26 of the first 74 prisoners to be exonerated by DNA evidence in the 1990s had been convicted largely on the basis of a supposed match between their hair and hair follicles found at the crime scenes. In 1997, a Vancouver, Washington, man was convicted of murder largely on the strength of a Dutch expert's claim that he was 100% confident that an ear print found at the crime scene was made by the defendant, even though no peer-reviewed studies confirm the validity of ear print comparison. As of 2005, ear print analysis is still used in Europe, and the European Commission is conducting research in hopes of supporting or denying its validity. The FBI asked the National Academy of Sciences (NAS) to conduct an examination of voice-print technology, which is premised on the theory that a spectrograph can produce a unique pattern for an individual's speech, but the NAS concluded that the theory had not been validated. Firearm identification has come under similar scrutiny because while some of the marks found on a crime scene bullet are unique to the individual gun, other marks are shared by bullets fired from the same model of gun. Further, different brands of bullets can take on identifying marks differently, even though they have been fired from the same gun. In the early 2000s, research was under way to give firearm identification testimony more precision, especially in measuring error rates.

The judiciary began to show similar skepticism in 1999. Massachusetts Federal District Court judge Nancy Gertner assumed the role of gatekeeper that year when she refused to allow a forensic handwriting expert to testify as to the authorship of a stick-up note and restricted the expert to noting points of similarity between the note and the accused robber's handwriting. Said Gertner, "one's handwriting is not at all unique in the sense that it remains the same over time, or uniquely separates one individual from another." In 2001, a federal court in United States v. Saelee said that the testing that has been done on handwriting analysis "raises serious questions about the reliability of methods currently in use." In 2002, a federal judge in Philadelphia refused to admit a fingerprint comparison based on his belief that its techniques had not been scientifically validated (he later reversed this decision). The controversy this aroused followed on the heels of a February 1999 report issued by the National Institute of Justice , the research arm of the U.S. Justice Department, saying that the "theoretical basis" for fingerprint comparison "has had limited study and needs a great deal more work." A new study of the science behind fingerprint comparison was scheduled to begin in early 2005.

Although judges and others are demanding more scientific evidence from forensic scientists, few are willing to dismiss these branches of forensics as pseudoscience altogether. Many judges are, however, less shy about branding as pseudoscience some other branches of forensics, including forensic animation and forensic odontology .

A new branch of forensics, forensic animation, creates computerized illustrations of the events of a crime. The technology was first used in a 1984 New York car accident case. In 1992 it was used to convict a San Francisco man of murdering his brother. It has also been used in product liability and baby-shaking cases. By the early 2000s, over a hundred firms were specializing in the creation of forensic animations. Typical of these was a 72-second animation used to convict a Scranton, Pennsylvania, man accused of shooting his wife. The video broke down the crime second by second, illustrating the angle from which the shots were fired, where they entered the body, and the like. Judges like forensic animation because of its efficiency; a video can show in minutes what might take a day or more to establish with traditional witness-stand testimony. Prosecutors like it because it brings a crime to life in a way that such phrases as "posterior exit wound" uttered by dour scientists do not. Others dismiss the technology as a form of pseudoscience for at least three reasons. First, the animation creates an aura of accuracy and precision, similar to the 650 quadrillion knife blades mentioned above, about the reconstruction of events that is often based, at best, on human analysis and interpretation of physical evidence. Second, the animation fills in blanks in the sequence of events that cannot really be known. And finally, noting that in functioning as executive producers of such videos, many attorneys admit it is possible to manipulate camera angles or lighting to achieve a desired effect that may mislead a judge or jury.

Also coming under severe fire is bite mark evidence offered by forensic odontologists. These experts originally limited their efforts to identifying crime or disaster victims through dental records, but after gaining recognition as a division of the American Academy of Forensic Sciences in 1970, they began to branch out into criminal investigations. Relying on low-tech tools like putty to make impressions of bite marks and plaster casts of a suspect's teeth, as well as such high-tech tools as image-enhancing software to make bite mark features more visible, they have testified at hundreds of trials, often involving such crimes as rape, murder, and child abuse, where bite marks are often found on the victims. Some have gone so far as to say that bite marks are as good as fingerprints for identifying a criminal. However, says David Faigman of the University of California Hastings College of Law, "Bite marks probably ought to be the poster child for bad forensic science." He and others point to numerous cases in which convictions have been won after forensic odontologists testified with high certainty that bite marks identified defendants who were later exonerated by DNA evidence. Noting that the field lacks a firm research base, they point to studies in which forensic odontologists in controlled settings arrived at false conclusions anywhere from a quarter to two-thirds of the time and sometimes even failed to identify marks caused by something other than a human bite.

The American Academy of Forensic Sciences, founded in 1948, serves to promote accurate scientific practices within the forensic science community through education, professional association, and with its peer-reviewed publication, the Journal of Forensic Sciences.

see also Animation; Expert witnesses; Federal Rules of Evidence; Frye standard; Handwriting analysis; Odontology; U.S. Supreme Court (rulings on forensic evidence).