The Twelfth Card

the receipt, prints on the merchandise. They’re all the same. Only, the thing is, they’re small, too small to be from a six-foot-tall man. A petite woman or a teenage girl, the clerk’s, I’d say. I see smudges too. I’d guess the unsub wiped his own off.”
    While it was difficult to remove all the oils and residue left by human fingers, prints could be obliterated easily by a brief rubbing.
    “Run what you’ve got through IAFIS.”
    Cooper lifted copies of the prints and scanned them. Ten minutes later the FBI’s integrated automated fingerprint identification system had verified that the prints did not belong to anyone on file in the major databases, city, state and federal. Cooper also sent them to some of the local databases that weren’t linked to the FBI’s system.
    “Shoes,” Rhyme announced.
    Sachs produced the electrostatic print. The tread marks were worn, so the shoes were old.
    “Size eleven,” Cooper announced.
    There was a loose correlation between foot size and bone structure and height, though it was tenuous as circumstantial evidence in court. Still, the size suggested that Geneva had probably been right in her assessment that the man was around six feet tall.
    “What about a brand?”
    Cooper ran the image through the department’s shoe-tread database and came up with a match. “Bass-brand shoes, walkers. At least three years old. They discontinued this model that year.”
    Rhyme said, “The tread wear tells us he has a slightly turned out right foot, but no noticeable limp and no serious bunions, ingrown nails or other malades des pieds. ”
    “I didn’t know you spoke French, Lincoln,” Cooper said.
    Only to the extent it helped an investigation. This particular phrase had come about when he was running the missing-right-shoes case and had spoken on a number of occasions to a French cop.
    “What’s the trace situation?”
    Cooper was poring over the evidence collection bags containing the tiny particles that had adhered to Sachs’s trace collector, which was a sticky roller, like the kind for removing lint and pet hair. Rollers had replaced DustBuster vacuum cleaners as the collector of choice for fiber, hair and dry residue.
    Wearing the magnifiers again, the tech used fine tweezers to pick up materials. He prepared a slide and placed it under the microscope, then adjusted the magnification and focus. Simultaneously, the image popped up on several flat-screen computer monitors around the room. Rhyme turned his chair and examined the images closely. He could see flecks that appeared to be bits of dust, several fibers, white puffy objects, and what looked like tiny amber shells shed by insects—exoskeletons. When Cooper moved the stage of the scope, some small balls of spongy, off-white fibrous material were visible.
    “Where did this come from?”
    Sachs looked over the tag. “Two sources: the floor near the table where Geneva was sitting and beside the Dumpster where he was standing when he shot Barry.”
    Trace evidence in a public place was often useless because there were so many chances for strangers unconnected to the crime to shed material. But similar trace being found in two separate locations where the perp had been suggested strongly that it had been left by him.
    “Thank you, Lord,” Rhyme muttered, “for thy wisdom in creating deep-tread shoes.”
    Sachs and Thom glanced at each other.
    “Wondering about my good mood?” Rhyme asked, continuing to stare at the screen. “Was that the reason for the sidelong look? I can be cheerful sometimes, you know.”
    “Blue moon,” the aide muttered.
    “Cliché alert, Lon. You catch that one? Now, back to the trace. We know he shed it. What is it? And can it lead us to his den?”
    Forensic scientists confront a pyramid-shaped task in analyzing evidence. The initial—and usually easiest—job is to identify a substance (finding that a brown stain, for instance, is blood and whether it’s human or animal, or that a piece of lead is a bullet fragment).
    The second task is to classify that sample, that is, put it in a subcategory (like determining that the blood is O positive, that the bullet that shed the fragment was a .38). Learning that evidence falls into a particular class may have some value to police and prosecutors if the suspect can be linked to evidence in a similar class—his shirt has a type-O-positive bloodstain on it, he owns a .38—though that connection isn’t conclusive.
    The final task,