I explained. “The killer’s double-stranded DNA fragments were broken, or denatured, into single strands. In more simplistic terms, they were unzipped like a zipper. The probe is a solution of single-stranded DNA of a specific base sequence that’s labeled with a radioactive marker. When the solution, or probe, was washed over the nylon membrane, the probe sought out and bonded with complementary single strands-with the killer’s complementary single strands.”
“So the zipper is zipped back up?” she asked. “But it’s radioactive now?”
“The point is that his pattern can now be visualized on X-ray film,” I said.
“Yeah, his bar code. Too bad we can’t run it over a scanner and come up with his name,” Wesley dryly added.
“Everything about him is there,” I continued. “The problem is the technology isn’t sophisticated enough yet to read the specifics, such as genetic defects, eye and hair color, that sort of thing. There are so many bands present covering so many points in the person’s genetic makeup it’s simply too complex to definitively make anything more out of it than a match or a nonmatch.”
“But the killer doesn’t know that.”
Wesley looked speculatively at me.
“That’s right.”
“Not unless he’s a scientist or something,” Abby interjected.
“We’ll assume he isn’t,” I told them. “I suspect he never gave DNA profiling a thought until he started reading about it in the papers. I doubt he understands the concept very well.”
“I’ll explain the procedure in my story,” Abby thought out loud. “I’ll make him understand it just enough to freak him.”
“Just enough to make him think we know about his defect,” Wesley agreed. “If he has a defect . . . That’s what worries me, Kay.”
He looked levelly at me. “What if he doesn’t?”
I patiently went over it again. “What continues to stand out to me is Matt Petersen’s reference to ‘pancakes,’ to the smell inside the bedroom reminding him of pancakes, of something sweet but sweaty.”
“Maple syrup,” Wesley recalled.
“Yes. If the killer has a body odor reminiscent of maple syrup, he may have some sort of anomaly, some type of metabolic disorder. Specifically, ‘maple syrup urine disease.'”
“And it’s genetic?” Wesley had asked this twice.
“That’s the beauty of it, Benton. If he has it, it’s in his DNA somewhere.”
“I’ve never heard of it,” Abby said. “This disease.”
“Well, it’s not exactly your common cold.”
“Then exactly what is it?”
I got up from my desk and went to a bookcase. Sliding out the fat Textbook of Medicine, I opened it to the right page and set it before them.
“It’s an enzyme defect,” I explained as I sat back down. “The defect results in amino acids accumulating in the body like a poison. In the classic or acute form, the person suffers severe mental retardation and/or death at infancy, which is why it’s rare to find healthy adults of sound mind who suffer from the disease. But it’s possible. In its mild form, which would have to be what the killer suffers from if this is his affliction, postnatal development is normal, symptoms are intermittent, and the disease can be treated through a low-protein diet, and possibly through dietary supplements-specifically, thiamine, or vitamin B1, at ten times the normal daily intake.”
“In other words,” Wesley said, leaning forward and frowning as he scanned the book, “he could suffer from the mild form, lead a fairly normal life, be smart as hell-but stink?”
I nodded. “The most common indication of maple syrup urine disease is a characteristic odor, a distinctive maple syrupy odor of the urine and perspiration. The symptoms are going to be more acute when he’s under stress, the odor more pronounced when he’s doing what stresses him most, which is committing these murders. The odor’s going to get into his clothing. He’s going to have a long history of being self-conscious about his problem.”
“You wouldn’t smell it in his seminal fluid?” Wesley asked.
“Not necessarily.”
“Well,” Abby said, “if he’s got this body odor, then he must take a lot of showers. If he works around people. They’d notice it, the smell.”
I didn’t respond.
She didn’t know about the glittery residue, and I wasn’t going to tell her. If the killer has this chronic odor, it wouldn’t be the least bit unusual for him to be compulsive about washing his armpits, his face and hands, frequently throughout the day while he’s exposed to people who might notice his problem. He might be washing himself while at work, where there might be a dispenser of borax soap in the men’s room.