The video screen went gray and digital seconds began to count. Mary worked other buttons on her control panel, and a bright orange spectrum suddenly appeared on the screen against a background of vivid blue. She moved the cursor and expanded what looked like a psychedelic stalagmite.

“Let’s see if there are other metals.”

She made more adjustments.

“Nope,” she said. “It’s very clean. Think we got our same suspect again. We’ll call up magnesium and see if there’s an overlapping of lines.”

She superimposed the spectrum for magnesium over the one for our sample, and they were the same. She called up a table of elements on the video screen, and the square for magnesium was lit up red. We had confirmed our element, and although I had expected the answer we got, I was still stunned by it.

“Do you have any explanation as to why pure magnesium might be transferred to a wound?” I asked Chan as Marino returned.

“Well, I told you my pipe story,” she replied.

“What pipe?” Marino said.

“Only thing I can think of is a metal shop,” Chan went on. “But I would think that machining magnesium would be unusual. I mean, I can’t imagine what for.”

“Thanks, Mary. We’ve got one more stop to go, but I’m going to need you to let me have the shaving from the Warrenton case so I can take it over to firearms.”

She glanced at her watch as the phone rang again, and I could only imagine the caseload awaiting her.

“Right away,” she generously said to me.

The firearms and toolmarks labs were on the same floor and were really the same section of science, since the lands and grooves and firing pin impressions left on cartridge cases and bullets were, in fact, the toolmarks made by guns. The space in the new building was a stadium compared to the old, and this sadly spoke to the continuing deterioration of the society beyond our doors.

It was not unusual for schoolchildren to hide handguns in their lockers, or show them off in the bathrooms, and carry them on the school bus, it seemed, and it was nothing for violent offenders to be eleven and twelve years old. Guns were still the top choice for killing oneself or one’s spouse, or even the neighbor with the constantly barking dog. More frightening were the disgruntled and insane who entered public places and started blasting away, explaining why my office and the lobby were protected by bulletproof glass.