Doctrines and Deductions

Our resident forensic scientist appears preternaturally gifted to his colleagues. Actually he's just more thoughtful.

The doctrine of scene examination is that attentive, dispassionate observation, gathering minute details – ‘trifles’, as Sherlock Holmes called them – will reveal the events that have taken place. Gradually, the information accrued shifts the balance from opacity to clarity, from incomprehension to understanding, like building up a digital image, pixel by pixel. The amount of information at most scenes is overwhelming and confusing, and the opportunities for error and misunderstanding are great. So it all has to start slowly and steadily. At the beginning no one knows the answers but they emerge, as the collective knowledge of everyone present distils information from a combination of experience, skills, imagination and guesswork. Holmes sees it all instantaneously because his act is a trick, his cleverness comes from the skill of his omniscient creator. But sometime reality mimics art; and on these rare occasions, the interpretation of a crime scene can be instantaneous, like a 3D image snapping into focus when you put on those special specs.

I am standing in the bedroom doorway of a bedsit tenement flat in a smart area of Edinburgh. A man in his late forties has been murdered and I have been asked to examine the bloodstain patterns at the scene. This isn’t typical murder territory. Maybe the location is the first, weak but significant signal that I pick up unconsciously. The doorway is in the corner of the room. Diagonally opposite me is another door to a small kitchen. There is a double bed in the middle of the wall facing me. The body of a man is sitting on the floor with its back against the wall to my right. I walk over to the body: he has been battered and his face is covered in blood but there is no blood staining on the wall behind him. Two CSIs, suited and gloved, busy themselves with their own work. “Who moved the body?” I say to no one in particular. Both CSIs turn towards me and then to each other. There is no response. This hasn’t occurred to them.

426 sperm exhibit

I move closer to the body and look at the floor in the gap between the bed and the wall that leads to the kitchen. There is a small bedside table by the bed, next to the kitchen doorway. On the floor, there are some flattened and bloodstained cardboard boxes between me and the bedside table. Iain, a perennially miserable photographer, is standing in the doorway photographing the kitchen. “Have a look under that bedside table,” I say to him. “There should be some blood there.” He gives me his usual, ‘I’m really busy can’t you do it yourself?’ look, before he realises I would need to walk over the bloodstained cardboard boxes. He gets down on his knees and shines a light under the table. “How did you know it was there?” he asks. “Splashes?” I ask. “Yes,” he replies.

Splashes on the underside of the table could only have come from below, so I know the victim must have been attacked on the floor near the bedside table. I have made a working assumption that all the blood is from the victim. I haven’t yet searched the place but I haven’t picked up anything that suggests otherwise.

As I leave the scene, I pass my provisional conclusions about the blood pattern to the crime scene manager. The victim was battered on the floor near the bed and then the body was moved and propped up against the wall. I don’t know why the body was moved; something inchoate is nagging me. There are always uncertainties, often too many to worry about.


“Who moved the body?” I say to no one in particular. Both CSIs turn towards me and then to each other. There is no response. This hasn’t occurred to them

The next morning in the lab, Allan, the lab technician comes to see me. John, an experienced scientist, is with him. Allan looks at John for support. “We found semen on the oral swab in that murder case,” he says. I look at John and he nods. The police were working on the theory that the motive for the murder was a dispute over payment with an electrician who was doing work in the flat. They hadn’t yet traced the electrician. I never bought that theory but since I couldn’t explain why, I just got on with the work. The revelation of the oral swab puts a different complexion on the case and the police need to know as soon as possible. One of my innovations in the lab to try to spread the crazy workload and deal with the backlog of cases was to get Allan to do some casework examinations, even though a strict interpretation of the legal protocols forbade this. Allan handed me the microscope slide and I examined it: there are definitely sperm present. Allan’s concern is now that he will end up in court and he isn’t qualified or trained to give evidence. He thinks he would fall foul of a smart defence lawyer and that this will backfire on the lab, especially me. There is also the spectre that it could wreck the case; this is more worrying.

427 forensic investigator

“Did you follow the procedure we agreed?” I ask Allan. “Yes.” I get the swab from the freezer and check his notes: packaging, description, spot tests. They are all fine. I take the swab out from the tube. Part of it has been sampled but, as I instructed, he had left at least half of the swab untouched. I take another sample from the swab and prepare it for microscopic examination. It only takes me a few seconds to find sperm. Now I am the witness, not Allan – there will be no need to mention him. I phone one of the investigators on the team that I know well and tell him the news. There is silence. “You sure? This is going to wake everybody up.” “I’m sure,” I say.

Some days later the DCI in charge of the scene examination unit came to see me. Alec was a capable and affable character; we had worked well together on a few cases. We chatted for a bit then he went quiet. “How did you know there was blood under the bedside table?” he asked. I explained that, if the victim had been attacked on the floor by the bed, there could have been blood under the table. “But how did you know it was there?” I said: “I didn’t, I just thought that was the most likely place for it.” My powers of deduction, as Holmes might call them, had been the subject of debate and speculation for several days in the crime scene unit, and the DCI had taken it on himself to clear it up for everyone.

Meanwhile, the scientific findings from the swab that transformed the case from a typical murder to an unusual sexual murder seemed to pass everyone by.