by Ken Goddard
“But that means—” David looked horrified.
“Based on your SEM work, it appears that the subject—or someone very near to his location—did discharge a firearm just before he was killed, but that firearm was almost certainly a rifle,” Bobby completed.
“Well, David,” Grissom said with a tight grin after a long moment of silence that filled the analytical chemistry lab, “thatcertainly changes the situation a bit, no?”
14
“IT WAS MY FAULT,” Catherine said glumly.
As she addressed Grissom, she was in the process of taking a new swab out of her right lab coat pocket, and gently ran the white fibrous tip across the blood-splattered dash of the truck. She then snapped the protective plastic cap closed, broke off the thin wooden stick, and marked the cap with the next “located item number” in order. After making a couple of quick notations in her notebook, Catherine dropped the collected swab into her left lab coat pocket…where it joined the other twelve swabs that she’d taken from the interior of the truck cab.
“Not necessarily,” Grissom demurred.
“Of course it was! I could have swabbed the pistol right there at the scene, or at the very least made sure that David swabbed both exterior sides, the barrel,and the chamber before he gave it to Brass,” Catherine replied. “So now we don’t know if the pistol was in the vehicle before the shooting started or dumped there afterwards.”
“There are a lot of things we don’t know yet,” Grissom said, “but I think we’re starting to make some significant progress.”
The entire graveyard CSI team was now assembled in the lab’s spacious two-bay garage. Sara was helping Catherine by documenting the interior truck cab with her strobe-mounted digital camera, while Warrick sat at a small portable table between the two bays and adjusted the laptop-projected 2-D image of the campsite scene on the far garage wall. At the front end of the still-hoisted truck, Greg was on his knees, using some of the data that Sara had generated to reposition some of the wooden dowels through the now correctly matched holes. Approximately half of the dowel-ends were now also marked with colored pieces of tape to indicate the impact path of a lead pellet or a copper-jacketed bullet.
Satisfied with the work in progress, Grissom walked over to the adjacent garage bay, where Nick was busy adjusting the lab’s portable laser scanner—once again attached to the cherry picker mounted on the roof of one of the lab’s black Denali SUVs—over the successfully patched and reinflated left and right rear tires from the bullet-riddled red truck. The exterior points where bullets had penetrated the walls and treads of the now-patched and reinflated tires were visually marked with small bright pink dots.
“Okay, I’m ready to scan,” Nick called out to Warrick, who quickly brought up another window on his laptop.
“Do it,” Warrick said, and then watched approvingly as the digital images of the two tires slowly appeared on the laptop screen.
Once the scan was completed, Warrick said: “Okay, time to turn them over.”
Nick quickly flipped the two tires over onto their opposite sides, and then set the scanning operation into motion a second time.
“Okay, that should do it,” Warrick called out, watching with a satisfied smile as the second pair of tire images filled his laptop screen.
“I’m truly impressed by the new software, I really am; but I have to confess I still can’t help thinking that you and Nick are cheating just a bit,” Grissom commented as he stood over Warrick’s left shoulder and watched him manipulate the two sets of two-dimensional images with a series of program tools that gradually turned the data into a pair of amazingly lifelike three-dimensional tires.
“You were really expecting us to run dowels through those four sets of bullet holes, patch the tires around the dowels, carefully inflate the tires to a few pounds of pressure, mount them back on the truck, and then use several hundred trig calculations to figure out where Grayson and the truck were in correct alignment for each shot?” Warrick was staring at his boss in disbelief.
“That’s how it would have been done once,” Grissom replied, a little self-consciously. “It’s a solidly established protocol, going well back into the sixties. Criminalists like John Davidson from the San Bernardino Sheriff’s Lab worked very similar scenes using a slide rule to do all the math.”
“A slide rule, to do 3-D trig? Jesus, how long didthat take?” Warrick asked, looking horrified.
“Several weeks, as I recall,” Grissom said. “And granted, it would have taken us a while to make all of the relevant calculations, but—”
“Well, that’s pretty much how I’m going to do it, too,” Warrick said cheerily as Nick approached the portable table and stood over his right shoulder, watching his partner continue to manipulate the pair of 3-D tire images until they finally appeared mounted on a digital rear axle assembly, “except I’m not going to make my head hurt in the process. I say let the computer do all of the hard work.”
As Warrick continued to work, the laptop screen split into two sections, each showing one of the digital tires mounted on the axle with a screen-wide pair of coordinate lines crossing at ninety-degree angles at the precise center of each hub.
“There,” Warrick said with evident satisfaction. “Now watch this.”
As Grissom and Nick looked on, Warrick caused four digital dowels to appear, and then transected them—one at a time—through the sixteen pink dots on the digital tires that the scanner program seemed to have no trouble locating.
“How do you know which holes each of those dowels go through?” Grissom asked.
“I don’t know…yet,” Warrick answered as he expanded the screen image out so that it now included a graphical 2-D version of the scanned campsite—the two large boulders, the twelve shooter-position cones, a dotted outline where the truck had come to a stop, and a pair of roughly parallel dotted lines leading to the campsite that represented the truck’s tire tracks.
“But there are only two entry and exit holes on each tire—looks like Grayson was a pretty decent shot. That means there are only four possible combinations of the two dowel-vectors, entering and then exiting each tire,” Warrick explained. “I’m going to try each possible combination, one at a time, and see what we get in the way of correlation.”
“What are those four red circles to the left of that upper boulder?” Grissom asked.
“Those are rough position estimates of where Grayson was standing when he fired each of his four shots, based on his boot prints in the sand and the location of the four casings from his weapon,” Warrick said. “The height of the end of his pistol barrel from the ground when he was shooting at the tires is approximately sixty inches.”
“How accurate are the x and y position estimates?”
“Plus or minus two feet. Not all that accurate, because Grayson was running and shooting, which would pretty seriously impact the landing-points of the ejected casings,” Warrick replied, “but good enough for what we’re doing here.
“We’ll start with the first possible combination of dowel-vectors as I’ve got it shown here,” Warrick went on, “then I’m going to move the rear axle assembly—I’m really moving the entire truck, but I only care about the rear tires, so that’s all I’m going to show on the screen—back along the tire track…like so.”
“Wow,” Greg said.
Grissom looked up, observing that Catherine, Sara, and Greg had stopped what they were doing and were all now watching the digital show being displayed on the far garage wall.
“Okay,” Warrick explained, “what you’re seeing is the rear axle assembly reversing its path from its position where we found it at the campsite back to the road, the two tires traveling approximately eight feet every full revolution. And as that happens you can see that each of the two dowel-vectors is moving also; but at different rotational angles because of their different orientations to the moving center axis of the axle itself.”
“But you can’t really see that from an overhead
view,” Nick pointed out.
“No, you can’t,” Warrick said, “but if you look at it from a 3-D side view”—he made a couple of selections and the view shifted accordingly—“you can see how the dowels and their extended vectors rotate differently, narrowly or widely—depending on the angle the bullets entered and exited the tires. If you can imagine the truck jacked up slightly, so that the tires rotate but don’t move forward, like this”—another mouse click brought the rotating tires up off the electronic road—“you can see that one dowel-vector forms a cone with awide base and the other dowel-vector forms a cone with a muchnarrower base.”
“Ah, I see. But if you allow the tires to drop back down to the road and move forward,” Nick said as he reached over Warrick’s shoulder and clicked the mouse again, “you can see that the imaginary end of the two dowel-vectors form a pair of arcs—one large and one small frog hop—that disappear underground for two different time intervals…and then continue to reappear and disappear, forming either a few large hops or a large number of much smaller hops as the truck continues to move.”
“Sweet,” Greg commented enthusiastically.
“But this might not be the correct combination of vectors,” Grissom said.
“And, in fact, it’s not,” Warrick agreed, “because when you shift the 3-D side view to include the four approximate locations of Grayson when he fired those four shots”—the computer screen view shifted again, and now showed four sticklike figures standing in the four circles aiming a stick gun at a slightly downward angle—“there’s no 3-D alignment with the two left rear tire dowel-vectors and the first two gun-barrel-aligned shooting positions for Grayson. In fact, it’s not even close.”
Warrick shifted the screen view again to show that the two dowel-vector lines from the left rear tire missed the linear-bullet-path from the “stick-figure-gun”—a thin red line drawn from the gun toward the general location of the passing truck—by several feet in each case.
“And that can’t be right,” Warrick went on, “because the barrel of Grayson’s pistol had to be lined up on one of the dowel-vectors coming out of those tires at the precise moment of each shot; that’s just basic physics, not to mention common sense.”
“Hey, wait a minute, how do you know Grayson fired the first two bullets at the left rear tire, and not the right one…or maybe one at the left tire andthen one at the right?” Sara protested.
“Well, first of all, because that’s what he said he did,” Warrick replied, “and secondly, from his vantage point at those first two circles, he couldn’t possibly see and hit the truck’s right rear tire, because it was being blocked out by the left rear tire and the truck bed.”
“Oh…okay, that makes sense,” Sara agreed as she examined the scene diagram displayed on the wall more closely.
“But we always want to hear what the evidence has to say, rather than the suspects and cops,” Warrick said, “so now we’ll go back to the final resting position of the truck again”—the computer screen shifted accordingly—“change the dowel-vectors to the second possible set of connected-bullet-hole combinations, backtrack again all the way to Grayson’s first shooting position, and—”
“Oh my God, it matches,” Catherine whispered.
“And then we move forward again to his second shooting position,” Warrick went on.
“And you have an almost perfect alignment with the second left rear tire dowel-vector,” Nick said, the awe evident in his voice.
“And continuing on to the third and fourth dowel-vectors,” Warrick finished, and then said nothing else as all six CSIs watched the slowly moving and rotating dowel-vectors line up almost perfectly with Grayson’s third and fourth shooting positions.
“And there we have it,” Warrick finally said after several seconds of silence, “the starting point we need to reconstruct the shooting scene: four precisely known positions of the truck when Grayson fired his four shots…because that’s where the truckhad to have been at those four specific moments in time.”
“I take back my comment about you and Nick cheating,” Grissom said breathlessly. “You’ve clarified the initial events at our scene in a way that can only be described as elegant. I think John Davidson would have been proud…not to mention more than a little envious of your technological advantages.”
“Here, here,” Catherine added her congratulations.
“Actually, I hate to be the one to rain on our parade,” Nick said hesitantly, “but I think we just made one aspect of our reconstruction a lot more confusing.”
“Why do you say that?” Grissom demanded, his forehead and eyebrows furrowing into a painful-looking expression.
“If we assume Grayson’s four shooting positions are accurate, as they almost have to be, based on the path of the truck,” Nick explained, reaching over Warrick’s shoulder to hit a function key and then pointing up at the 2-D overhead scene image displayed on the far garage wall, “he has no possible line of sight on Jane Smith during any of his shots, because she’s completely blocked out by the ‘female facilities’ boulder; so Graysoncouldn’t have been the one who shot her.”
“You’re right,” Grissom acknowledged. “So where does that take us…back to a rifle shot from the subject in the truck?”
“I guess that would be possible.” Warrick created a pair of direct lines from two of the truck positions—based on Grayson’s third and fourth shooting positions—to the position where Jane Smith claimed to have been crouching when the truck first roared into the campsite. “The driver of the truck clearly would have had a line of sight on her at the onset—at least for a brief moment before the boulder blocks her out. But a one-handed, high-powered rifle shot through the passenger-side window, while he’s driving at high speed through sand with the other hand, and heading directly toward five other well-armed narcs? That really doesn’t make a lot of sense.”
“Not unless he was willing to commit suicide just to nail her,” Nick added, “which really doesn’t sound like the guy Fairfax and Holland were describing.”
“I suppose you never want to underestimate the illogical behavior of a psychotic killer,” Grissom said softly, “but I agree: it doesn’t make sense…which means we need to take another look inside that truck.”
“Again?” The expression on Catherine’s face was pained. “I must have collected at least a hundred swabs from that cab by now, and those chunks of brain splattered across that back window and seat are definitely starting to get ripe. What else can we do in there?”
“You’ve all heard me say, many times I’m sure, that a well-performed crime scene investigation is always comprised of a mechanical process and a thinking process,” Grissom replied. “And how easy is it—when you’re facing a huge amount of evidence, as we certainly are on this case—to fall into the trap of collecting evidence mechanically without really thinking about what you’re seeing and smelling and otherwise sensing?”
“So?” Catherine said uneasily.
Grissom smiled sympathetically, remembering that he’d observed his senior CSI swabbing by rote several times while working the truck, visibly forcing herself to ignore the surrounding gray-white splatterings of brains. He guessed she was now wondering what she might have missed while going through the motions.
“So I think we need to do a little more thinking about what we’re seeing…or, more to the point, what we’renot seeing,” Grissom replied carefully. “Which means I think we need to do something that John Davidson would have almost certainly done before he ever considered pulling out his slide rule,” he added as he removed a folding knife from his lab coat pocket and flicked open the sharp blade.
“Cut his wrists?” Greg said.
“No,” Grissom replied. “This time, we reallyare going back to the basics.”
15
TWENTY MINUTES LATER, in the chemistry section of the laboratory, Gil Grissom and the other CSIs watched as Greg Sanders carefully placed an irregular piece of bloodstained fabric—cloth that Gri
ssom and Catherine, a few minutes earlier, had cut out of the right interior door panel of the truck—onto a large chemically treated piece of smooth-surfaced filter paper.
Working quickly now, Greg removed a large swatch of cheesecloth—cut roughly the same size as the piece of bloodied fabric and the filter paper—from a beaker filled with 15 percent acetic acid, and then gently arranged the dripping cloth over the piece of fabric. Finally, he picked up a hot steam iron, pressing it across the entire surface of the cheesecloth…and then immediately recoiled as the hot acetic acid vapors rose around his face once again, ripping into his now extremely sensitive sinuses.
“Very nicely done, Greg,” Grissom said approvingly. “Your technique is definitely improving.”
“You couldn’t prove it by me,” the young CSI said, looking thoroughly miserable as tears rolled down his cheeks. “What did you call this test again?”
“The modified Greiss test for nitrite residues,” Grissom said. “When smokeless gunpowder in a cartridge is detonated, a great deal of nitrites are produced that would normally be very distinct and visible as powder burns or powder pattern residues on a nearby surface. But if those burns or pattern residues happen to get deposited on a dark or discolored surface—such as the bloody seat fabric, door panel, and roof panel fabrics of our subject’s truck—then these burns and patterns may not be distinctly visible.” Grissom paused. “Surely you learned this in class?”
“I’m pretty sure that was the lab a couple of us skipped out on to go see Marilyn Manson,” Greg said. “I seem to remember we all agreed that we wouldn’t be missing much, because there had to be a more modern test for nitrites.”
“Oh, there is,” Grissom said. “But old-fashioned as it may be, the Greiss test has certain advantages—the primary one being range and density of the color reaction. When the hot acetic acid vapors penetrate the fabric in question, bright orange spots are produced on the paper that indicate a significant buildup of nitrites.”