One of the more intractable problems in the criminal justice system is how to evaluate expert testimony. Who gets to offer their expertise to juries, and how can the courts ensure that expertise is reliable? Exoneration records teem with charlatan experts who did incalculable damage, both by sending innocent people to prison and by allowing the guilty to go free.
M. Chris Fabricant, director of strategic litigation for the Innocence Project, has been on the front lines of these fights for more than a decade. In his fierce and absorbing new book, “Junk Science and the American Criminal Justice System,” Fabricant chronicles the battles he and his colleagues have fought to unravel a century of fraudulent experts and the bad court decisions that allowed them to thrive.
The age of the dubious court expert dawned with the rise of early 20th-century progressivism, a movement that, laudably, sought to stamp out political corruption and replace it with science and expertise. But the progressive fondness for expertise could at times extend into quackery — often laced with racism. Perhaps the best example is Sir Francis Galton, a Victorian-era polymath often cited as the father of fingerprint identification. Galton was a mathematician, a scientist and something of a celebrity. But he was also a believer in phrenology and eugenics (he actually coined the term) and supported the involuntary sterilization of groups he considered undesirable.
Judges have long been the gatekeepers of expertise. But judges are trained in law, not science, and these are two very different disciplines with almost contradictory objectives and methods of analysis. The law prioritizes consistency and reliability; science is constantly changing based on new evidence and new discoveries.
For a long time, the two fields didn’t intersect much. The criminal justice system developed the field of forensics, a series of disciplines glossed with the veneer of science but mostly not subjected to the rigors of the scientific method, such as double blind testing or peer review. For decades, judges have allowed trials to be polluted by fraudulent and pseudoscientific testimony in fields such as arson, hair and carpet-fiber matching, forensic pathology, and ballistics.
The credibility of some forensic disciplines took a hit in the 1990s when DNA testing — real science — began to show that some prisoners those experts had deemed undeniably guilty were, in fact, innocent. Fabricant’s book picks up about 20 years after DNA testing became commonplace, as the courts continue to grapple with this fundamental square peg/round hole problem: How to reconcile science with law.
The book focuses on three of Fabricant’s cases involving bite mark analysis, a field that shot into popular culture during the trials of Ted Bundy in the 1970s and hit its heyday in the 1990s. Bite mark analysis rests on two unproven premises: The first is that every person’s teeth leave a unique bite mark. The second is that human skin is capable of recording and preserving those marks in a way that allows them to be matched to a specific person.
Fabricant documents howPeople v. Marx, an obscure California appeals court ruling in 1975 with an unusual set of facts, set in motion a formidable body of law establishing bite mark analysis as court-approved expertise. Paradoxically, in that case the court itself acknowledged that bite mark matching isn’t science. (The judges instead ruled that in that specific case, the bite mark evidence was common sense, allowing them to skip a scientific review.) That ruling has since become the urtext for a cascade of decisions authorizing a variety of scientifically dubious disciplines. The ensuing jurisprudence has been the legal equivalent of the childhood game of “telephone.” Shortly after Marx, other court decisions cited it, misstating its holding to authorize a new application of bite mark analysis and similar techniques. Another wave of rulings then cited back to those, roping in yet new applications and new methods of analysis. Each new citation was a misapplication of the original ruling, each expanded the use of suspect techniques, and each citation only further cemented the original, already-erroneous ruling as canon.
Yet as in other disproven areas of forensics, the courts have stubbornly refused to catch up. Just this past February, an Alabama judge upheld a murder conviction won primarily because of bite mark testimony, despite the fact that the dentist who testified at trial has recanted. A month later, a Michigan man was convicted of child abuse in part because state expert witnesses claimed to have found bite marks on the child that could only have been left by the man’s chipped tooth. While that sort of theory may seem plausible to a public conditioned by CSI reruns, the legal record is littered with convictions of supposedly oddly toothed men who were later proved innocent.
The most damning thing here isn’t the exonerations, but that the courts have failed to course-correct after learning of them. Fabricant points out that in at least three states — Wisconsin, Massachusetts and Mississippi — the controlling precedent establishing bite mark analysis as credible ended up upholding the conviction of someone later proved to be innocent. That is, in the very case that still authorizes the use of bite mark analysis in those states — and to which lower courts must defer today — the bite mark analyst was wrong.