Scene of the Crime (29 page)

blood from when he took his injured pet to the veterinarian? Blood type—can this be the blood of the victim or the suspect, or is it that of someone else? It is important to remember that in all cases, the older the blood is, the less information will be obtainable from it. In blood more than a year old, it may not be possible to obtain much more than the species and the ABO type; the DNA fingerprint may persist for years, but the older the blood, the less likely that any test results will be reliable.

Of course, the investigator and the laboratory will at times be looking for different information from blood found at the scene of the crime and from blood found later on the person, clothing, vehicle, or other possessions of the suspect.

Obviously if the blood at the scene is that of the assailant and, as usual, the crime is discovered promptly, with reasonable luck the blood type and the DNA fingerprint of the assailant can be obtained. But even if the blood belongs to the victim, there are many things it can reveal about the suspect and about the manner in which the crime occurred. Quite a lot of research has centered on this matter, and a terrific recent book is
Interpretation of Bloodstain Evidence at Crime Scenes,
by William G. Eckert and Stuart James. It is part of the Elsevier Series in Practical Aspects of Criminal and Forensic Investigations; although it's the only one of the series I've needed to consult, the entire series (listed inside the front endpapers of the book) looks splendid for a crime writer's personal library as well as for an evidence technician's library. Of course, they should all be available through interlibrary loan.

Although all aspects of bloodstains are important, Dr. Paul Kirk, who wrote a pioneering book on blood at the crime scene, contends that "No other type of investigation of blood will yield so much useful information as an analysis of the blood distribution patterns" (Eckert and James 11-12). Kirk, who was involved with the Sheppard appeals, testified in 1955 that he

was able to establish the relative position of the attacker and victim at the time of the ... beating. He was able to determine that the attacker administered blows with a left hand, which was significant in that Dr. Sheppard was right-handed.

(Eckert and James 12)

As a result of his testimony, interest in bloodstain evidence — which had been substantial throughout the history of criminal investigation—grew considerably, and forensic scientists as well as investigating officers realized even more the need for careful studies of the characteristics of blood in various situations. Up to that time, each individual investigator, working on his or her own, would decide what the bloodstains appeared to indicate, sometimes on the basis of experiments with beef or chicken blood (which does not have exactly the same characteristics as human blood) and sometimes on the basis of sheer guesswork. Working under a government grant, H.L. MacDonnell did several painstaking studies, which were published in 1971 and 1973. By 1983, the International Association of Bloodstain Pattern Analysts had been organized, and the study continues. Eckert and James suggest that careful study of bloodstains can provide the following types of information:

• Source of the blood—human or animal? Which human or animal?

• Relative positions of persons and objects in the area at the time of the attack.

• Distances the blood flew, and speed.

• Whether impact was from sharp or blunt object.

• Number of impacts.

• Elapsed time between impact and study.

• Movements of persons and objects after the attack.

By providing this information, the study can help to determine which possible witnesses are telling the truth; can provide additional means of judging time of death; and can help to sort out findings from other investigative and laboratory work.

For a more precise discussion of bloodstains, see the entire Eckert and James book, particularly the section beginning on page thirteen.

But in order for any of these desirable results to occur, the investigator at the scene has the primary responsibility for—what? For seeing to it that s/he fulfills the duties that are always the primary responsibility of the investigator on the scene: making careful notes; making careful photographs (preferably color, preferably with a measuring device included in every photograph); and taking careful, triangulated measurements. The investigator must
always
remember that no color film is fully dependable for showing subtle gradations in color, so notes are critical; furthermore, photographs

not done very carefully may distort the truth. (We've all seen photos in which someone's feet, placed in the foreground, appear ten times their real size.)

Cameras and Film

At the time that I entered police work, the Albany Police Department was still using a Speed Graphic. That's the camera you see reporters and police photographers using in old movies—the one that's so tough that reporters could knock somebody in the head with it and then go on taking pictures. When Chief Summerford first instructed me to learn to use it, I was intimidated by the very sight of that camera.

Once you learn how to use it, however, there's practically nothing you can do to mess up pictures on it; it's far less fussy than many cameras. The huge (four-by-five-inch) negative allows enlargements for courtroom use with practically no grain, whereas a 35mm negative enlarged to eleven-by-sixteen is almost always going to look somewhat grainy. Its film packs and sheet films also prevent waste: If I use only four shots on a roll of film and need the pictures this afternoon, the other shots are wasted; if I use only four shots on a film pack, I can pull those four out and develop them and still have the other twelve shots left. And in a small darkroom, sheet film is far easier to work with blind than roll film.

But for all practical purposes, the day of the Speed Graphic is gone. Even black-and-white film for it now costs a small fortune, and I doubt color film is even available except through incredibly expensive special orders. Most police photography now is done almost entirely in color with 35mm cameras and film.

What kind of color film? A good photographer—or a writer intending to play tricks with photography in fiction—will take the time to read all available information on all films and determine which is the best to use now. Nobody can possibly say which is going to be best forever, because manufacturers are constantly improving film and processes.

In general, most crime-scene photographers use whatever camera the department supplies, and keep a personal camera and more departmental film in their car so that if they get a call in

the middle of the night, they can go straight to the scene without having to detour by the police station.

It is important to remember that photography, when produced incompetently or with intent to mislead, particularly in a blood-spatter situation, can cause serious problems.

In general, police photography does not use filters of any kind. It is important to be able to swear, in court, that what the photograph shows is as nearly as possible
exactly
what the photographer saw. But most photographers know a few tricks. One is that if you shoot black-and-white panchromatic film through a filter the same color as your subject, that color seems considerably lighter in the picture; if you shoot through a complementary color filter, the color in the scene seems considerably darker. Thus, by using a red filter, you could effectively do away with a lot of the blood in the scene; by using a green filter, you could darken the blood.

In crime-scene investigations, it just doesn't happen. But in fiction? Ah, in fiction ... what can
you
do with the possibilities?

But read a good camera book before you start on those possibilities. In this area, errors can make you look stupid.

Type el Bleed-Spatter Patterns

The type of spatter pattern is determined by several factors, including the force with which the blood falls (is it dripping from a vein, spurting from an artery, slung from a weapon raised to make another blow, oozing from a dying victim?), the distance it falls, the type of surface it lands on, and whether it lands vertically or at an angle. If all these factors are considered, it is possible to trace the blood back to its converging point, just as one would do by extending the point a bullet impacted back through a hole in the wall where it penetrated, to determine where it was fired.

Some of these things have been reduced now to a formula — not one simple enough to do by hand, but one which can be put on any computer that can work with Basic. This program is included in the appendix to the Eckert and James book.

Eckert and James, and all other blood pattern investigators, warn against trying to make the blood reveal too much. Insufficient evidence is insufficient evidence, no matter what it consists of, and

overinterpretation of insufficient evidence can lead to serious errors. (That's a terrific idea for use in fiction.)

Fingerprints, toolmarks, footprints, fabric imprints, and so forth can be made in blood, as well as in any other substance. In such a situation, the pattern must be carefully studied, as well as anything the blood itself reveals. That is, careful measurements and photographs are essential, and the item carrying the print, if possible, must be sent to the laboratory.

We've already talked a lot about fingerprints. Let's go on now and see what can be determined about some other items.

Tiremarks

From tire tracks, it is possible to determine the size of the vehicle, how heavily it is loaded, and the make of the tire. Each year, manufacturers make available to police agencies photographs of their new products, and data bases of this information are available to forensic scientists. If any tire manufacturer fails to cooperate, it is always possible to buy a tire of the type in question and make a data base entry.

When a suspect tiremark is first photographed and then cast in plaster of Paris, it is thereafter treated by the lab exactly as if it were a footprint.

Because each tire on each vehicle wears individually, if the suspect vehicle is located fairly soon—within a few hundred miles or so, and before the tire is changed—it is possible to say that this particular tire track was made by this particular tire and—usually— on this particular vehicle.

Tools and Toolmarks

What are toolmarks? They are the marks—most often various types of striations, or ridged, linear markings—made by any object other than the weapon used in the commission of a crime. If at all possible, the toolmark itself—the doorframe that carries the marks of the prybar, the safe and safe door which have been opened— should be transported to the laboratory. If this is completely impossible, then dental molding should be used to create an exact impression of the mark. Great care must be exercised to prevent distortion.

At the laboratory, technicians using comparison microscopes can almost always determine whether this mark was made by this suspect tool. If the suspect tool is not available, the lab can provide some information that will help investigators look for the tool; however, the likelihood of their being able to provide exact descriptions, brand names, and so forth is fairly small.

If you are curious as to how this would work, take a piece of lightweight but fairly wide metal of some sort and twist it in two. Then, using a magnifying glass, examine the ends where the metal parted. What you are looking at, in vastly simplified form, is what the lab will work with.

Footprints

If you've read Arthur Upfield's Australian mysteries, you've read a lot about tracking, trackers, what they can determine from footprints. I've never met anybody who could tell as much about footprints as Upfield's half-Abo detective, but I'm not saying it's impossible. Some people may be able to tell that much.

If you've read P.D. James's
Devices and Desires,
you've come across a more recent—and a more reasonable in terms of what is generally possible—use of footprints. In that case, because the Bumble brand sneakers with their bee on the sole were brand new, the brand and size were all anyone could determine. Generally, if the print is good and the shoes are distinctive, as sneakers usually are, the size and brand can be determined. How does this work? Every year, or with every design change, shoe manufacturers submit to law-enforcement laboratories information on the patterns on the sneaker soles. If—as may happen—some manufacturers decline or neglect to submit these patterns, the examiners simply purchase a pair of the sneakers in question. So books or computerized data banks of the patterns on distinctive shoe soles—available only to laboratory technicians, not to the general public—are constantly kept up to date, the same way data banks of tiremarks are kept current.

But no matter how smooth and nondistinctive the soles began, the shoes begin to differ as they begin to wear. The more they wear, the more different they become; by the time they have had fairly heavy wear, a good forensic scientist given the photograph or cast of the print and the shoe that made it, can say with absolute certainty that this shoe made this footprint. (Of course, that does not necessarily mean that the suspect was wearing the shoe, so that's always something writers can play with.)