Scene of the Crime (30 page)

The patterns of bare feet, generally, don't tell much except the size of the feet. But in a few rare instances, the footprint pattern— which, like fingerprints and palm prints, consists of friction ridges— can be determined. In those cases, once a suspect is developed, an identification can be made as easily as by fingerprints.

I missed my one chance to make a footprint identification, when a barefoot burglar walked on top of furniture in a furniture store. He left perfectly good fingerprints another place, and he was too grotty for me to want to footprint him. I've kind of regretted missing the opportunity, but every time I think of his feet and his state of health ("I gots the syphs," he told me), I remember why I stuck with the fingerprints.

Fabric Impressions

The burglar had crawled through the kitchen exhaust fan into the restaurant, picking up an enormous quantity of grease on the way. Once in, he sat down briefly on an unopened crate of paper towels, leaving a perfect impression of the seat of his denim jeans. Shortly thereafter, a suspect was developed by other means. Doc and I couldn't make a positive identification of the grease print of his rear end, but we were sure enough to send the suspect jeans and the top of the crate to the laboratory for examination, and shortly thereafter the laboratory was sure enough to make the jury sure enough to get a conviction.

That's only one use of fabric impressions. As unlikely as it might sound, the intense impact of an automobile hitting a person may be sufficient to leave an impression of the person's clothing on the bumper; or blood may instantaneously splash out, soak the clothing, and leave an impression in blood of the clothing on the bumper. (Of course, in that case, the victim's blood alone may be enough for an identification, but on the other hand, it may not.)

Forensic Geology

Remember the scene in a Sherlock Holmes story where Holmes, observing the mud stains on Watson's trousers and shoes, tells Watson all the places he has been that day? Normally, in a small area— small in this case including the average city—there won't be quite that many different types of soil; certainly there won't be that many that can be distinguished by the naked eye. (And yet, when I was working as a state-sponsored amateur on an archaeological dig that was carbon-14 dated to more than 1,300 years ago and that covered less than 2,000 square feet, we had four different and highly distinctive soils, including sand, red clay, loam, and a yellow clay that apparently had been hauled a considerable distance and used to make a pavement. Certainly anybody could distinguish the shoes of a person who had been on that dig from those of one who had not.) At the very least, forensic geologists can usually determine whether the soil from this shoe or this tire
could
have come from a suspect location; when that determination is combined with what might have been learned from the shoe prints or the tire tracks at that location, the likelihood that this suspect is indeed the perp increases considerably.

In some cases, such as the situation of a rare, imported soil, the possibilities increase geometrically. In George Chesbro's
Second Horseman Out of Eden,
a letter from an abused child to Santa mailed in New York contains small amounts of a type of soil found only in the Amazon rain forest. Once the soil's source is determined, Mongo and his long-suffering brother are off on a crusade to discover how the envelope wound up in New York and where the child is located.

In real life, the results aren't usually quite that dramatic. But the possibilities are always there, and many are the times that I have used the evidence vacuum to collect microscopic evidence from the floorboard of a suspect vehicle to send it, with samples of soil from the area where the crime occurred, to the laboratory; many are the times the reports have come back telling me that the soil found in the floorboard of the car, presumably deposited there from the shoes of the suspect, could have come from the sample area. "Could have" is usually about the best the scientists can do, so this type of evidence normally must be combined with other evidence.

Fireclay

Fireclay combines the work of the forensic geologist with the work of the forensic paleontologist. So first—what is fireclay?

It is the insulating substance packed in the walls of a safe to protect the contents from fire and heat as long as possible. Fireclay is composed of sand, fine clay, and other minerals, and it almost always includes diatomaceous earth—earth that was once at the bottom of the sea. It contains fossil remnants of many microscopic sea creatures, and microscopic examination can almost always determine whether the fireclay on the suspect's shoes, in his trouser

cuffs, and rubbed into his gloves is from the same source as the fireclay in the safe lining.

Safecrackers!

Like bank robbers and forgers, safecrackers used to be the cream of the crop of criminals. Now amateurs have taken over all three fields.

Despite the tales about safecrackers who used sandpaper on their fingers and then could feel when the tumblers dropped, so that they could open the safe using the dial, such safecrackers are extremely rare. Most often safes are peeled, burned or blown.

A
blown
safe has had holes drilled into it and explosives inserted into the holes. When the explosives are detonated, theoretically the safe blows open. More often the safe's contents are destroyed as well. Really good safecrackers don't blow safes.

A
burned
safe is opened when the part surrounding the dial is destroyed by an oxyacetylene blowtorch and the dial is removed; a similar technique can be used to remove the trunk's lock and retrieve lost trunk keys to your car. Some safecrackers cut all the way around the door.

A
peeled
safe is a professional job. The first time you see a peeled safe, you can scarcely believe your eyes. It looks like a sardine can cut open with an old-style blade can opener by a person on a fishing trip—except that the "blade" was a prybar and the "sardine can" may have three layers of walls including two inches or more of metal and six inches or more of fireclay.

Forensic Botany

Forensic botany sounds unlikely. What does the study of plants—other than marijuana and opium poppies—have to do with crime?

A whole lot. Like forensic geology, forensic botany can help to determine who has been where.

Pollen, leaves and flowers are all useful. In the landmark 1960 Australian kidnapping of Graeme Thorne, the victim's body was found six weeks later, wrapped in a rug tied into a bundle.

Scientists were able to determine from fungus spores found on the boy's shoes that he was murdered within hours of his abduction.

(The spores would have required six weeks to reach maturity.) But far more important, they found many fragments of a pinkish mortar and building stone, and among the large quantity of plant matter found in or on the bundle were large (by laboratory standards) quantities of debris from two different types of cypress tree. One was common, but the other was extremely rare—so rare that when they finally found a house that was built of the pink stone and had both of the cypress trees in its yard, and when they then learned that the previous occupant of the house, a man who had moved away on the very day of the kidnapping, had already been considered a suspect for other reasons, they were sure they had the perp.

And indeed they did. Stephen Leslie Bradley confessed and then retracted the confession, but the evidence was overwhelming. He was convicted and sentenced to life in prison.

Not all forensic botany is that impressive, and it can rarely stand alone. But when it is put together with the results of forensic geology, it can be extremely useful both as an investigative tool and as a court exhibit.

Hair

Human hair is somewhat problematical. Time after time, brilliant laboratory work has invented a method of positively establishing that this hair came from this body, and time after time, the method has been proven unreliable. DNA fingerprinting may help, but even it may be less positive than one would wish, quite simply because hair itself is dead. Only the hair bulb—the hair root—itself can be positively "fingerprinted," and even then only if it is at least halfway fresh—that is, before the bulb has either totally dried out or begun to rot. Hair evidence rarely includes the bulb, unless it was pulled out by the roots, as does sometimes happen in a violent crime.

However, hair evidence can be used to rule out many things. Species can almost always be determined, and it is usually possible to distinguish head hair from pubic hair. Race can frequently be determined from hair, and certainly it is commonly possible to determine that this particular hair did
not
come from this particular head.

But in general, the best positive identification that can be made right now is that this hair
could
have come from this person.

You will, by the way, find older books written while a method now obsolete was in use, that insist that this or that method is certain. At the time that this book is being written—the very beginning of 1992—there is no definite method of determining which hair came from whom, unless the root bulb is intact.

Sorry.

Check with the FBI next year. The situation is likely to change.
Fibers

Fibers, like hairs, botanic evidence and geological evidence, are somewhat circumstantial. The laboratory can determine quite a lot, including composition, origin (animal—wool or mohair? Plant— cotton or linen? Synthetic—nylon or orlon?), color, and often even dye lot, but it usually cannot say positively that this fiber came from this carpet or article of clothing and no other.

Even so, quite a lot of information can be derived. When the Shroud of Turin was subjected to intensive examination, much of the work was somewhat similar to that which might be done on crime-scene materials. A basic tenet of criminalistics is that when two items come in contact—whether the items are automobiles or human beings—there will be exchange of microscopic particles. (This is part of the reason for the very careful examination of the person and clothing of both victims and suspects.) This tenet was applied to the Shroud, because the assumption was that if it had been in Palestine 2,000 years ago, despite its history since then some pollen and so forth from that area and that time should still be clinging to it. Such pollens and dust particles indeed were found, and no trace of pigments that would have been used in painting were located. But other, less explicable, materials were present. Among the numerous submicroscopic pieces of fiber clinging to it were some pink fibers from a synthetic material that had never been used for anything other than women's girdles. Investigators confessed themselves baffled by that one. The only reasonable explanation was that an earlier investigator or photographer had come into contact with such a girdle, carried off fibers from it on his clothing, and later rubbed some of those fibers onto the Shroud.

Paint and Varnish

There are three situations in which these are likely to be useful. The first is when a victim has been assaulted or murdered in one location and then moved to another. In that case, the presence of paint or varnish (or any other chemical substance, such as motor oil or printer's ink) on the clothing or body may lead back to the location where the attack occurred, which in turn may lead to a suspect who had access to that spot.

The second situation occurs when the paint or varnish dust is in the air of the known crime scene, and this dust can be sought on the clothing of the suspect.

The third—and most common—use for paint occurs in a hit-and-run or an automobile murder. Very often paint chips off, and although these paint chips may convey nothing but color to the layman, they convey far more to the laboratory technician. Ford's blue car and Cadillac's blue car and Toyota's blue car are not the same blue. They contain slight or great color differences, and great differences in composition, layering, and so forth: An expensive automobile may have many layers of paint baked on, a cheap automobile may have no more than three or four layers. Of course, if a car has been repainted, either professionally or by a teenager with a paint brush and a left-over half-bucket of house paint, these facts also may be determined by the layers of paint. Next time you or a neighbor has a minor fender bender, have a look at some of the paint chips before the fender is fixed, and see what you can tell just with a small magnifying glass.

Glass

Glass is another circumstantial material. But it can prove a lot.

Scientists maintain files of the color, chemical composition and fractile characteristics of automobile headlight glass, so that a fragment found at the scene of a hit-and-run will help to determine within a few possibles the make and model of an automobile. When that information is combined with the paint chips often found with the glass, the color of the vehicle also becomes available.

Given several pieces of glass, scientists can determine from which side of the glass the impact came, whether it was a blunt impact or a sharp impact, and sometimes the force of the blow.

If the investigating officer or technician has made the usual careful records, it is almost always possible to determine whether glass was broken from the inside or the outside, even if an "inside job" was covered up by breaking glass and then putting the fragments inside to make it appear that the glass was broken from the outside.