Brandon L. Garrett - Autopsy of a Crime Lab

Imagine that you have been selected to sit on a jury in a criminal trial. An expert takes the stand. He emphasizes his credentials as a senior fingerprint examiner at the Federal Bureau of Investigation (FBI), in Quantico, Virginia, the preeminent crime lab in the country. A series of explosions had killed over 190 people in a terrorist attack. The expert proceeds to confidently describe a forensic hit, comparing a fingerprint of the defendants to a print found on a bag of detonators in a white van parked near the scene. The expert explains that he studied high-resolution images of the prints on a computer screen, identified fifteen points they shared, and reached a firm conclusion: a 100 percent identification. Next, he asked two experienced colleagues to review the prints: the chief of his unit and a retired FBI examiner with thirty-five years of experience. Each of the three experts agreed 100 percent with his conclusion.

The judge instructs you, as a juror, to carefully observe all of the evidence in the case. The judge tells you that to convict you must be certain beyond a reasonable doubt that the defendant was the culprit. Would you convict?

Thats not my fingerprint, your honor, says the defendant, in response to this evidence.

What ... the judge responds. It wasnt your fingerprint?

If it is, I dont know how it got there, he insists. It is not my fingerprint.

In the real case, Brandon Mayfield, a Portland, Oregon lawyer, pleaded for his freedom in an Oregon federal courtroom. Federal agents testified that they identified his fingerprint on a plastic bag with detonators found near the bombing of four commuter trains in Madrid, Spain, that killed 193 people and injured about two thousand more. The judge sided with the FBI and ordered Mayfield detained as a material witness to terrorism. Mayfield knew that he was innocent. He had never set foot in Spain. He had converted to Islam years earlier, and the FBI theorized that perhaps he had formed an allegiance to militant Islamic groups and traveled under a fake name. His case would come to reshape the course of forensics, but only after he faced the prospect of indefinite detention and the death penalty.

Would you convict a person if the only evidence in the case was a fingerprint comparison? What if it was a bite mark, a drug test, or a DNA test? Before making the momentous decision to convict a person, you should ask how reliable the evidence is. Forensic evidence refers broadly to evidence in legal matters that involves scientific methods; my focus in this book is on the wide array of forensic evidence used in criminal cases. What is most surprising is that many forensic examiners do not use methods that are based on solid scientific research. Indeed, with the exception of DNA testing, the experts who link evidence to particular defendants at criminal trials cannot give you a straight answer to the question, How reliable is your evidence? Techniques like fingerprinting have been used for over a hundred years. Surely, someone must know how reliable they are. Yet not only is reliability untested and unknown, but the experts do not candidly admit to the judge and the jury that deep uncertainty lies at the foundations of their work. They do not admit that no one has carefully tested the reliability of the methods they use or the work they do on routine cases. Nor do they admit that the crime lab where they work lacks a rigorous testing program. Instead, forensic analysts testify in court just like the actors on popular forensics shows: they claim to find a perfect match. Take, for example, an episode of the popular show CSI: Miami, where the investigators, like in Mayfields case, had just a single fingerprint.

The FBI analysts in Brandon Mayfields case were even more certain: they were 100 percent certain. They were so certain that when Spanish authorities issued a report with a negative conclusion, contrary to the FBIs fingerprint identification, the FBI fingerprint analysts forcefully disagreed and flew to Madrid, Spain, to present their findings, with blown-up photos illustrating their work. The FBI placed Mayfield under twenty-four-hour surveillance, and then they arrested him. Mayfields lawyer counseled him that he could be detained indefinitely and might face the death penalty. Then, on May 20, 2004, the prosecutor stood up in court and told the judge something unexpected: that morning the government received some information from Spain which casts some doubt on the identification. Spanish authorities determined completely that the print belonged to a known Algerian terrorist. The FBI agreed to release Mayfield, dropped all charges a few days later, apologized to Mayfield, and a federal investigation followed.

Our crime labs need an autopsy. The episode profoundly harmed Mayfield and his family. The failure of these FBI agents brought home how little we know about the reliability of forensic evidence. We need to know why these errors occur. After all, fingerprints have been used in court for over a hundred years. Fingerprint examiners insisted for decades that they had an error rate of zero. If three experienced fingerprints experts could get it so badly wrong, in a high-profile case, then how reliable is fingerprinting? How about all of the other forensics? The problem cried out for a serious scientific inquiry. A mini-autopsy did occur in response to the Mayfield case itself, when the U.S. Department of Justice wrote a lengthy report identifying specific problems with the work done in Mayfields case. However, the investigators did not try to answer the most fundamental question that you would want answered if you were sitting on a jury: How reliable is a fingerprint comparison? No scientific studies had been done on the question. The investigators briefly noted in their report that according to critics, the basic premises of fingerprint

A few lone voices, mostly in academia, had raised reliability concerns for years, but without any success in the courts. Particularly when DNA testing became more common in the 1990s, leading scientists, law professors, social scientists, and a few defense lawyers began to ask what research supported the traditional non-DNA forensics. They were ignored. In 1993, the U.S. Supreme Court issued its landmark decision in Daubert v. Merrell Dow Pharmaceuticals, Inc. , holding that federal judges must act as gatekeepers to ensure that experts use reliable methods. Lawyers expected that judges would finally scrutinize forensic science in court, particularly after many states adopted this federal rule. A few judges hesitantly raised reliability concerns about fingerprinting, but the FBI shut them down with confident assertions that such techniques were foolproof.