The Twelfth Card

and the ultimate goal of all forensic scientists, is to individuate the evidence—unquestionably link this particular bit of evidence to a single location or human being (the DNA from the blood on the suspect’s shirt matches that of the victim, the bullet has a unique mark that could be made only by his gun).
    The team was now low on this forensic pyramid. The strands, for instance, were fibers of some sort, they knew. But more than a thousand different fibers were made in the United States annually and over seven thousand different types of pigments were used to color them. Still, the team could narrow down the field. Cooper’s analysis revealed that the fibers shed by the killer were plant based—rather than animal or mineral—and they were thick.
    “I’m betting it’s cotton rope,” Rhyme suggested.
    Cooper nodded as he read through a database of vegetable-based fibers. “Yep, that’s it. Generic, though. No manufacturer.”
    One fiber contained no pigments but the other had a staining agent of some kind. It was brown and Cooper thought the stain might be blood. A test with the phenolphthalein presumptive blood test revealed that it was.
    “His?” Sellitto wondered.
    “Who knows?” Cooper responded, continuing to examine the sample. “But it’s definitely human. With the compression and fractured ends, I’d speculate the rope’s a garrotte. We’ve seen that before. It could be this was the intended murder weapon.”
    His blunt object would be simply to subdue his victim, rather than to kill her (it’s hard, messy work beating someone to death). He also had the gun, but that would be too loud to use if you wanted to keep the murder quiet in order to escape. A garrotte made sense.
    Geneva sighed. “Mr. Rhyme? My test.”
    “Test?”
    “At school.”
    “Oh, sure. Just a minute . . . I want to know what kind of bug that exoskeleton’s from,” Rhyme continued.
    “Officer,” Sachs said to Pulaski.
    “Yes, m’ . . . Detective?”
    “How ’bout you help us out here?”
    “Sure thing.”
    Cooper printed out a color image of the bit of exoskeleton and handed it to the rookie. Sachs sat him down in front of one of the computers and typed in commands to get into the department’s insect database—the NYPD was one of the few police departments in the world that had not only an extensivelibrary of insect information but a forensic entomologist on staff. After a brief pause the screen began to fill with thumbnail images of insect parts.
    “Man, there’re a lot of them. You know, I’ve never actually done this before.” He squinted as the files flipped past.
    Sachs stifled a smile. “Not exactly like CSI, is it?” she asked. “Just scroll through slowly and look for something you think matches. ‘Slow’ is the key word.”
    Rhyme said, “More mistakes in forensic analysis occur because technicians rush than because of any other cause.”
    “I didn’t know that.”
    Sachs said, “And now you do.”

Chapter Six
    “GC those white blobs there,” Rhyme ordered. “What the hell are they?”
    Mel Cooper lifted several samples off the tape and ran them through the gas chromatograph/mass spectrometer, the workhorse instrument in all forensic labs. It separates unknown trace into its component parts and then identifies them. The results would take fifteen minutes or so, and while they waited for the analysis Cooper pieced together the bullet the emergency room doctor had removed from the leg of the woman whom the killer had shot. Sachs had reported the gun had to be a revolver, not an automatic, since there were no brass cartridges ejected at the scene of the shooting outside the museum.
    “Oh, these’re nasty,” Cooper said softly, examining the fragments with a pair of tweezers. “The gun’s small, a .22. But they’re magnum rounds.”
    “Good,” Rhyme said. He was pleased because the powerful magnum version of the rimfire 22-caliber bullet was rare ammunition and therefore would be easier to trace. The fact that the gun was a revolver made it rarer still. Which meant they should be able to find the manufacturer easily.
    Sachs, who was a competitive pistol shooter, didn’t even need to look it up. “North American Arms is the only one I know of. Their Black Widow model maybe, but I’d guess the Mini-Master. It’s got a four-inch barrel. That’s more accurate and he grouped those shots real tight.”
    Rhyme asked the tech, who was poring over the examination board,