"Got a minute?"

"As many as you like."

He waved me in and pulled a chair next to his, "It's about the Cherokee Deslardins case.

"Yes. I saw you at the scene. Why are you working that one?"

"I'm not, exactly. I was there because initial reports described a burned body. As it turned out the victim was not in bad shape."

"Not in bad shape? He looked like a still life in brain tissue."

"Well, yes. Actually, that's what I'd like to talk to you about. I was going to ask Dr LaManche but, of course, that's not possible right now"

He looked puzzled.

"The investigators working the Cherokee case are convinced it's a biker hit." I hesitated, unsure how to put my reservations into words. "I can't nail it down, but something about the scene struck me as being off."

"Off?"

I explained my assignment with Operation Carcajou, and what I'd seen at the briefing session.

"I realize I'm a novice, but maybe that's it. Maybe I'm seeing things through different eyes.

"And what do your eyes tell you?"

"That the Cherokee murder was sloppy."

"Anything else?"

"That the victim was sloppy. Apparently Cherokee admitted his killer. Does that sound like a former member freelancing drugs on gang turf?"

I didn't mention Dorsey, or his claims of innocenée. I figured the less said about my prison visit the better.

Gilbert looked at me a long time, then smiled.

"Claudel thinks you're an interfering pain in the ass.

"I think highly of him, as well."

He threw back his head and laughed, then his face grew serious.

"How much do you know about blood-spatter analysis?"

"Not much," I admitted.

"Ready for a crash course?"

I nodded.

"O.K. Here goes."

He leaned back and raised his eyes to the ceiling, no doubt deciding where to begin and how to condense years of training into a brief lecture. I could picture him doing the same for a jury.

"A free-falling drop of blood is spherical due to the effects of gravity and surface tension. Think about when you prick your finger Blood builds up on the down side until the drop is able to break free and fall. Seems simple, right?"

"'Yes."

"It's not. All kinds of opposing forces are at work. Gravity and the increasing weight of the blood are 'pulling' the drop downward. At the same time the surface tension of the blood is trying to reduce the exposed surface of the drop and is 'pushing' it upward."

He gestured quotation signs around the verbs.

"Only when the 'pulling' forces exceed the 'pushing' forces will the drop break free. Initially it's elongated, but as it falls the drop flattens due to air resistance. The attractive forces of surface tension within the drop cause it to assume a shape with the least amount of surface area. Thus, drops of blood are shaped like spheres, not like teardrops as they're usually drawn. And shape is one of the things we consider in spatter-pattern analysis.

"A blood spatter is produced as a result of a force striking static blood. It could be in a pool on the sidewalk, or inside a victim s head. When hit, the blood breaks into drops, called spatter, which travel through the air as spheres."

I nodded.

"When these spheres strike a surface they leave predictable types of trails. Bloodstain-pattern interpretation is concerned with examining stains produced by drops of blood that are not typical. The stains and trails have been altered in some way, usually by violent activity.

"The goal of bloodstain-pattern interpretation is to work backward from a crime scene and reconstruct the events that took place. What happened? In what sequence? Who was where? What weapon was used? What objects have been moved? To answer these questions we look at what has altered the drops of blood present.

"And it's very complex." He began ticking points off on his fingers. "For example, we have to take into account the properties of the target. Blood will act differently when striking a smooth versus a textured surface."

Tick.

"Shape. Since the ratio of a stain's width and length accurately reflects its angle of impact, regardless of striking surface, we look carefully at the shape of the stains.

Tick.

"Spatter size. Smaller or slower-moving forces produce large spatters, while larger or faster-moving forces produce smaller spatters.

He stopped, thumb pressed to his fourth finger

"Still with me?"

"We talk about low-, medium-, and high-velocity-impact spattering, although these terms are really relative."

"Give me examples."

"I'll do better than that. Come with me.

He led me down the hall to a stainless steel refrigerator and withdrew a one-liter bottle labeled Sang dtt boeuf

"Beef blood," he explained.

I followed him along a narrow side corridor to an unmarked door, and we entered a windowless room where large sheets of white paper were taped to most surfaces.

The small chamber looked like a massacre site. Blood was pooled along one baseboard, streaked and splattered on the walls, and dripping from various-sized spots at knee level in the far corner Above each stain I could see pencil notations.

"This is our blood-spatter experiment room," said Gilbert, placing the bottle on the floor "Watch"

He removed the cap, dipped a wooden rod into the blood, then allowed it to drop onto the paper under his feet.

"Low-velocity-impact spatters are associated with drops passively falling onto a surface. Dripping blood, for example. The characteristic spatter size is greater than three millimeters in diameter In these situations the blood is moving slowly, from normal gravitational pull to up to five feet per second."

I examined the small round stains he'd created.

"Medium-velocity blood spatter results from activities such as beatings, blunt trauma iniuries, or stabbings. The blood is moving faster, with a force velocity between five feet and twenty-five feet per second."

As he said this he poured a small amount of blood into a dish, signaled me to step back, then swung the rod into it. The blood flew up and struck the wall. Gilbert gestured me over and pointed to several of the stains. They were smaller than the ones at his feet,

"See these spatters? The size range for medium-velocity spatter is typically less, averaging between one and four millimeters in diameter."

He lay down the rod.

"But the spots aren't as fine as with high-impact spatters. Come look at this."

We moved to the far wall, where he indicated an area that looked as if it had been spray-painted.

"High-velocity-impact spattering means a force velocity greater than one hundred feet per second and results from gunshots, explosions, and mechanical accidents. It's more like a mist, with individual spatters averaging less than one millimeter in diameter

"But don't get me wrong. Not every spatter falls neatly into one of these categories. Blood that is splashed, cast off, or projected can really complicate a picture."

"How so?"

"These are actually forms of low- to medium-velocity spatter, but they differ from the ones I just described. For example, splashed blood results from someone stepping into already-pooled blood. This leaves long, narrow spatters surrounding a central stain, with very few round stains present.

"Projected blood results from someone running through, stamping into, or slapping a pool of blood. Or from arterial gushing, or beating a head on the floor Again there are long, spiny spattcrs radiating from a central stain. But in this case the borders of the central stain are also distorted.

"Blood cast off from a weapon leaves yet another pattern. Let me show you.

He went back to the rod, dipped, and swung it in an arc. Blood flew from the tip and struck the wall to his right. I drew close and studied the stain.