From Hellhound On His Trail: The Electrifying Account of the Largest Manhunt In American History, by Hampton Sides (Knopf Doubleday, 2010), Kindle pp. 238-239:
AT THE FBI Crime Lab in Washington, the fingerprint expert George Bonebrake spent the early-morning hours of April 5 poring over the contents of the package that had been couriered up from Memphis. A slight, fastidious man, Bonebrake was one of the world’s foremost authorities on dactyloscopy, the study and classification of finger and palm prints. Bonebrake had worked as a fingerprint examiner for the FBI since 1941. His was an esoteric profession within the crime-fighting universe—more art, it was said, than science, a closed world of forensic analysis predicated on a foundation of facts so incredible that a thousand bad TV detective shows over the decades had done little to diminish the essential mystery: that the complex friction-ridge patterns on human fingertips and palms, unique to every individual on earth, carry trace amounts of an oily residue excreted from pores that, when impressed upon certain kinds of surfaces, can be “raised” through the use of special dusting powders or chemicals—and then photographed and viewed on cards.
As far-fetched as the discipline seemed to most laymen, fingerprint analysis by 1968 had been the standard technique of criminal identification for more than half a century. It replaced a bizarre and not terribly accurate method of French origin called the Bertillon system, which required the careful measuring of a criminal’s earlobes and other anatomical parts. Fingerprinting wasn’t perfect, but it was the best system in existence for narrowing the pool of potential culprits in many situations. In many cases, fingerprinting was a godsend, providing the breakthrough that solved the crime.
In 1968, the FBI categorized fingerprints according to the Henry classification system, which was developed by Britain in the late nineteenth century. The system recognizes three primary friction-ridge patterns—arches, loops, and whorls. Loops, the most common pattern, are assigned a numerical value according to the number of ridges contained within each pattern found on each digit. Loop patterns can be further described as “radial” or “ulnar,” depending on which direction their microscopic tails point.
Bonebrake got started with his meticulous work shortly after dawn. Most of the prints that he found were fragments or smudges that contained little or no information of value. The twenty-dollar bills that Mrs. Bessie Brewer had provided yielded no usable prints whatsoever. Eventually, however, Bonebrake was able to lift six high-quality specimens from the Remington rifle, the Redfield scope, the Bushnell binoculars, the front section of the Commercial Appeal, the bottle of Mennen Afta aftershave lotion, and one of the Schlitz beer cans.
Most of these prints appeared to come from different fingers, but already Bonebrake could tell that two of the prints—those taken from the rifle and the binoculars—were from the same digit of the same individual. Both seemed to have been deposited by a left thumb, and, upon further study, the print pattern would turn out to be unmistakable: an ulnar loop of twelve ridge counts.
This was an important find. The FBI had the fingerprints of more than eighty-two million individuals on file—a number obviously too large to work with, as fingerprint examiners had to do all matching the old-fashioned way, by hand, eyeball, and magnifying glass. This tiny little detail, however, narrowed the search considerably: an ulnar loop of twelve ridge counts on the left thumb. Bonebrake’s task was still formidable, but now he had something definite on which to draw comparisons. He made large black-and-white blowups of all six of the latent prints, and then he and his team got started.
Far Outliers 