Opening a manila envelope, I withdrew three smaller envelopes made of transparent plastic. Two contained the feathers collected from Jennifer Deighton’s and Susan Story’s homicides, while a third contained a slide of the gummy residue from Eddie Heath’s wrists.
“This is the best one, it seems,” I said, pointing out the feather I had recovered from Jennifer Deighton’s nightgown.
He took it out of its envelope and said, “This is down a breast or back feather. It’s got a nice tuft on it. Good. The more feather you’ve got, the better.”
Using forceps, he stripped several of the branchlike projections or “barbs” from both sides of the shaft and, stationing himself at the stereoscopic microscope, placed them on a thin film of xylene that he had dropped on a slide. This served to separate the tiny structures, or float them out, and when he was satisfied that each barb was pristinely fanned, he touched a corner of green blotting paper to the xylene to absorb it. He added the mounting medium Flo-Texx, then a coverslip, and placed the slide under the comparison microscope, which was connected to a video camera.
“I’ll start off by telling you that the feathers of all birds have basically the same structure,” he said. “You’ve got a central shaft, barbs, which in turn branch into hairlike barbules, and you’ve got a broadened base, at the top of which is a pore called the superior umbilicus. The barbs are the filaments that result in the feather’s feathery appearance, and when they’re magnified you’ll find they’re actually like minifeathers coming out of the shaft.”
He turned on the monitor. “Here’s a barb.”
“It looks like a fern,” I said.
“In many instances, yes. Now we’re going to magnify it some more so we can get a good look at the barbules, for it is the features of the barbules that allow for an identification. Specifically, what we’re most interested in are the nodes.”
“Let me see if I’ve got this straight,” I said. “Nodes are features of barbules, barbules are features of barbs, barbs are features of feathers, and feathers are features of birds.”
“Right. And each family of birds has its own peculiar feather structure.”
What I saw on the monitor’s screen looked, unremarkably, like a stick figure depiction of a weed or an insect leg. Lines were connected in segments by three dimensional triangular structures that Downey said were the nodes.
“It’s the size, shape, number, and pigmentation of nodes and their placement along the barbule that are key,” he patiently explained. “For example, with starlike nodes you’re dealing with pigeons, ring like nodes are chickens and turkeys, enlarged flanges with prenodal swelling are cuckoos. These” – he pointed to the screen – “are clearly triangular, so right away I know your feather is either duck or goose. Not that this should come as any great surprise. The typical origin of feathers collected in burglaries, rapes, and homicides are pillows, comforters, vests, jackets, gloves. And generally the filler in these items comprises chopped feathers and down from ducks and geese, and in cheap stuff, chickens.
“But we can definitely rule out chickens here. And I’m about to decide that your feather did not come from a goose, either.”
“Why?” I asked.
“Well, the distinction would be easy if we had a whole feather. Down is tough. But based on what I’m seeing here, there are, on average, just too few nodes. Plus; they aren’t located throughout the barbule but are more distal, or located more toward the end of the barbule. And that’s a characteristic of ducks.”
He opened a cabinet and slid out several drawers of slides.
“Let’s see. I’ve got about sixty slides of ducks. To be on the safe side I’m going to run through all of them, eliminating as I go.”
One by one he placed slides under the comparison microscope, which is basically two compound microscopes combined into one binocular unit. On the video monitor was a circular field of light divided down the middle by a fine line, the known feather specimen on one side of the line and the one we hoped to identify on the other. Rapidly, we scanned mallard, Muscovy, harlequin, scoter, ruddy, and American widgeon, and then dozens more. Downey did not have to look long at any one of them to know that the duck we sought was being elusive.