The final task, 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 extensive library 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.”

“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, “What’d you mean by nasty?”

“Take a look.”

Rhyme, Sachs and Sellitto moved forward. Cooper was pushing around bits of blood-stained metal with the tweezers. “Looks like he made them himself.”

“Explosive rounds?”

“No, almost as bad. Maybe worse. The outer shell of the bullet’s thin lead. Inside, the slug was filled with these.”

There were a half dozen tiny needles, about three-eighths of an inch long. Upon impact, the bullet would shatter and the pins would tumble in a V pattern throughout the body. Though the slugs were small they’d do far more damage than regular rounds. They weren’t designed to stop an attacker; their purpose was solely to destroy internal tissue. And without the numbing effect of a large-caliber slug’s impact, these shells would result in agonizing wounds.

Lon Sellitto shook his head, eyes fixed on the needles, and scratched the invisible stain on his face, probably thinking how close he’d come to being hit with one of these slugs. “Jesus,” he muttered. His voice broke and he cleared his throat, laughed to cover it up and walked away from the table.

Curiously, the lieutenant’s reaction was more troubled than the girl’s. Geneva didn’t seem to pay much attention to the details of her attacker’s gruesome rounds. She glanced again at her watch and slouched impatiently.

Cooper scanned the largest pieces of the bullet and ran the information about the slugs through IBIS, the Integrated Ballistics Identification System, which nearly a thousand police departments around the country subscribe to, as well as the FBI’s DRUGFIRE system. These huge databases can match a slug, fragments or brass casing to bullets or weapons on file. A gun found on a suspect today, for instance, can quickly be matched to a bullet recovered from a victim five years ago.

The results on these slugs, though, came back negative. The needles themselves appeared to have been broken off the end of sewing needles, the sort you could buy anywhere. Untraceable.

“Never easy, is it?” Cooper muttered. At Rhyme’s direction, he also searched for registered owners of Mini-Masters, and the smaller Black Widows, in.22 magnum, and came back with nearly a thousand owners, none of whom had criminal records. Stores aren’t required by law to keep records of who buys ammunition and therefore they never did. For the time being, the weapon was a dead end.

“Pulaski?” Rhyme shouted. “What’s with the bug?”

“The exoskeleton – is that what you called it? That’s what you mean, sir?”

“Right, right, right. What about it?”

“No matches yet. What exactly is an exoskeleton?”

Rhyme didn’t answer. He glanced at the screen and saw that the young man was only a small way into the Hemiptera order of insects. He had a long way to go. “Keep at it.”

The GC/MS computer beeped; it had completed its analysis of the white blobs. On the screen was a peak-and-valley chart, below which was a block of text.

Cooper leaned forward and said, “We’ve got curcumin, demethoxycurcumin, bis-demethoxycurcumin, volatile oil, amino acids, lysine and tryptophan, theronine and isoleucine, chloride, various other trace proteins and large proportion of starches, oils, triglycerides, sodium, polysaccharides…Never seen that combination.”

The GC/MS was miraculous in isolating and identifying substances, but not necessarily so great in telling you what they added up to. Rhyme was often able to deduce common substances, like gasoline or explosives, just from a list of their ingredients. But these were new to him. He cocked his head and began to categorize those substances in the list that, as a scientist, he knew would logically be found together and which would not. “The curcumin, its compounds and the polysaccharides obviously fit together.”