Xo (Kathryn Dance 3)

Lincoln Rhyme regarded the chart closely. "Not good, not bad. Let's get to work."

Chapter 53

"ENTRANCE AND EXIT routes from the convention center?"

Shean explained, "There're twenty-nine of them, including the windows and infrastructure access doorways and loading docks. There were thousands of prints and samples of trace."

Lincoln Rhyme said, "Yes, yes, sometimes the problem is too much evidence, rather than not enough.... I'm glad you know the number of exits, Charlie. Good searching."

"Thank you, sir."

"Lincoln," he corrected absently, absorbing the chart.

Rhyme and Shean got to work. Dance had wondered if being a guest would temper Rhyme's edge but, clearly, no. When he learned that there were two different places behind Edwin's house where an intruder might have stood to spy, he asked which trace came from which area. The tags on the half dozen collection bags reported only: Trace evidence from behind E. Sharp's house, Woodward Circle West.

"Well, we didn't really differentiate them."

From Rhyme: "Oh." It was the same as a loud dressing-down. "Might want to think about that in the future."

Rhyme had once told Dance, "Where you find the clue is critical, vital. A crime scene is like real estate. It's all about location, location, location."

On the other hand, Shean had satisfied Rhyme's number-one requirement when it came to trace: isolating "unique" material that might have been shed by the perp. This was done by taking many samples from spots nearby: samplars, they were called. If certain materials differed from these indigenous ones they might have come from the perp.

Shean's officers had collected hundreds of samplars at all the scenes for comparison.

"That was competent," Rhyme said. One of his more enthusiastic compliments. He then said, "And now, the cigarette ash."

Stanning asked, "We'd like to know if the samples of ash match."

"Yes, well, they wouldn't match, of course." He turned to the young woman. "Matching is when two or more items are identical," Rhyme muttered. "Very few things actually match. Friction ridge--fingerprints and footprints, of course. DNA and--going out on a limb--the lands and grooves on slugs and extractor marks on the brass. Tool marks under rare circumstances. But as for trace? I could make the argument about some substances matching by analyzing half-life but that's on a nuclear level."

He turned his wheelchair and faced Stanning. "Let's say you find cocaine that's been cut with eighteen percent baking soda and two percent baby powder, and you have another sample that's cut with exactly the same substances in those proportions. They don't match but they're associated, and a jury can infer they came from the same source. Of course, in our case, it's possible that somebody could smoke the same cigarette at two different locations, miles apart on different days. But the odds of that are rather low. Wouldn't you say?"

"I would. Definitely." Stanning looked as if she'd decided not to make any more comments.

"You get a lot of convictions when you testify, I'd imagine," Shean offered.

"Nearly one hundred percent," Rhyme said, with only a veneer of modesty. "Of course, if the odds aren't good up front I recommend not going to trial. Though I'm not above bluffing somebody into a confession. Now, I need to run an inductively coupled plasma test."

Shean said, "Mass spectrometry. Well, we can do that."

"I'm so pleased."

"But--well, just curious--why that, if you're analyzing ash?"

"For the metals, of course," Amelia Sachs pointed out.

The CSU head tapped his forehead. "Trace metals in cigarette ash. Brilliant. I never thought of that."

Rhyme said absently, "It's the most definitive way to determine the brand and origin of cigarettes when all you have is ash. I vastly prefer a fleck of tobacco itself too, because then you can factor in desiccation and other absorbed trace substances. That can pinpoint location of storage and time." He added a caveat, "Up to a point."

Shean prepared the sample and ran the test and a short time later they had their answer.

Looking over the computer screen, Rhyme offered, "Zinc 351.18, iron 2785.74 and chromium 5.59. No arsenic. Yep, that's Marlboro."

"You know that?" Harutyun asked.

A shrug--one of the few gestures the criminalist was capable of--and one that he used with s