Aaron Elkins: Twenty blue devils

"Ah,” said Gideon appreciatively. Now he was the one getting the chowderhead forensics course. Turnabout time again, and richly deserved. “Then that settles it,” he said slowly. “Rudy didn't quite tell it the way it was, did he?"

"Indeed not,” Viennot said, twirling his cigar for emphasis. “And I think we can hypothesize with some confidence as to what his reason was, don't you, colleague?…Colleague?"

Gideon had taken the skull into his hands while Viennot was speaking and had turned it around to take his first careful look at the other side, the right side, the one with both the round entrance wound and the depressed fracture suffered when Tari struck his head on the hearth in falling. He traced his fingers over the network of cracks between them. Well, well…

"Colleague?"

"Hm?” Gideon surfaced. “Oh, I'm sorry. You were saying…?"

"That we might hypothesize with some confidence as to what actually happened."

"I don't think there'd be any point in that, sir."

The physician's mobile features contracted into a scowl. “No point?"

"In hypothesizing.” Gideon replaced the skull on the butcher paper. “I know what actually happened,” he said with perhaps a little more panache than was strictly required; it was a common failing with him at such moments.

It takes a ham to appreciate a ham, and, as Gideon thought he might be, Viennot was delighted. After an astounded silence during which the cigar stub hung pasted to his lower lip he barked with laughter. “You know!" he cried happily. “ How do you know?” He chomped down on the cigar and leaned expectantly forward, elbows on the table, his nose no more than a foot from the bone. Like every true man of science he was at his happiest when about to be instructed.

"I know,” Gideon said, “because cracks don't cross cracks."

Cracks don't cross cracks.

Once a year Gideon taught part of a week-long forensic seminar that the Smithsonian put on for law enforcement personnel from across the country. And one of the first tests of scientific observation that his students were faced with came in the form of a hard-boiled egg that had been briskly tapped in three places with the underside of a tablespoon, so that at the site of each stroke was a small indentation in the shell (not at all unlike a depressed fracture), with a network of hairline cracks radiating from it.

"Pretend,” Gideon would say, handing it over for their inspection, “that this is a human skull fractured in three places by blows from a blunt instrument. What I want you to tell me is, which is the first blow that was struck, which is the second, and which is the third?"

Sometimes they would figure it out on their own. More often they would be stymied. “How the hell are we supposed to know that?” some grumpy sergeant who hadn't wanted to be there in the first place could be depended on to mutter.

Which is when Gideon would say: “Cracks don't cross cracks."

Once that was understood, which never took long, it was a simple matter. One of the dents in the shell would have a network of cracks that was unimpeded; the spidery, radiating lines would extend until they simply ran out of steam and petered out on their own. That was the site of the first blow. The cracks emanating from another one of the dents would also run to their natural limits-except for those that ran into already existing cracks from the first one and were stopped dead by them. That was the second blow. And the cracks from the third dent would stop every time they came to a crack from either of the other two. That, necessarily, was the third blow.

What was true of eggshells was true of skulls. A crack could not leap across open space to the far side of an aperture and continue, no matter how narrow the cleft. And in the skull before them, as he now pointed out to the enchanted Viennot, two of the cracks coming from the bullet hole were clearly cut off by cracks radiating from the depressed fracture. Therefore, the depressed fracture already existed when the bullet entered; the crushing blow to Tari's head had come before he was shot, not after.

"Before he was shot, yes,” echoed Viennot, nodding. “And that means…"

That meant that Rudy had not merely been forgetful, or unobservant, or overexcited in reporting what had happened. Rudy, seemingly so helpless and distraught, had been lying through his teeth, coolly and calculatingly.

"This explains the incomplete exit wound on the other side too,” Gideon said, reconstructing the scene in his mind (minus the blood and brains). “Tari already had his skull cracked open before he was shot. He must have been lying on the floor unconscious or maybe barely conscious. Rudy bent down, put the gun next to Tari's right temple-"

"Yes, that's right, a point-blank wound."

"-and pulled the trigger. The pressure of the floor kept the bullet from exiting completely from the other side of his head."

He had been staring at the skullcap all the time he spoke, but now he looked up to meet Viennot's eyes. “He murdered him,” he said with the dreamy satisfaction of a man who had put in a hell of a good morning's work. Not that it wasn't about time he'd done something useful.

"Colleague,” said Viennot, leaning back in his chair, “I salute you."

Colonel Bertaud contained his admiration more successfully than Dr. Viennot had ("You're certainly full of surprises this morning."), but he quickly grasped the significance of the new information that Gideon had brought him, which was all that Gideon was really interested in.

"Thibault, call the hospital,” he said into his telephone in rapid French. “Find out what room Mr. Rudolph Druett is in. And bring my car around."

"I do see one difficulty, however,” he told Gideon in that silky voice. “Not insurmountable but a difficulty all the same.” He turned his swivel chair so that he could look out on the avenue Bruat. It was a little after 9 A.M. Papeete's rush-hour traffic, such as it was, was settling down. Only a few motor scooters and bicycles were on the street. “How do you propose that we should account,” he asked thoughtfully, “for Tari's having struck his head on the hearth in the first place? Tari was a giant, yes? Rudy is a slight man, no more than half his weight. Is it conceivable that he could knock him down or throw him to the floor?"

"I don't think he did. My guess is Tari never did hit his head on the hearth; that the wound was caused by something else."

The colonel swiveled back to face Gideon. “But we have his blood, his hair, on the hearth. Our laboratory confirms it."

"Here's what I think happened, Colonel: I think Rudy clubbed Tari with something-maybe with a poker from the fireplace. Maybe it was premeditated, or maybe there was an argument, I don't know. Something. Anyway, Rudy hit him over the head from behind, then shot him to make sure he was dead, then smeared his head against the hearth-and banged his own head against the wall a little too-to back up his story about Tari's trying to kill him and how the whole thing was an accident, and so on."

He glanced at the skullcap on Bertaud's desk (Gideon had carried it from the hospital in a paper sack). “If you think about the placement of the fracture-high up, back, and on the right side-you'll see it's just where you'd expect it to be if Tari had been crept up on from behind by a right-handed assailant."

"Ah, is that so?"

"Definitely.” Then after a moment: “Well, it's also where you'd expect it to be if Tari had hit his head on the hearth in falling, so it's hardly proof of anything, but at least it fits. But you know,” he added as the thought occurred to him, “if I could have a look at that hearth and the poker and anything else along those lines, I just might be able to match one of them to the fracture in the skull. If nothing else, I ought to be able to rule some things out. Do you-"