either by accident, deliberately, or because the situation is so bad it cannot be redeemed.
Often, detectives brought us pieces of broken glass, holding them carefully by the edges, to have the surfaces printed. In a case like that, generally the detective would lay the glass on the seat beside him in the car on the way in, and hand it to us with a separate evidence tag for us to attach later. This worked well; the car's seat covers were too stiff to damage any prints, and it would take us only minutes to print the item and attach the tag.
This Glass is Full of—Something
Now suppose you need to fingerprint a container that is full of an unknown liquid. You will eventually have to get an analysis of the liquid, so you can't just dump it. You can't fingerprint the container with the liquid in it, because examining an item while fingerprinting it involves turning it in different directions to get the light on it at different angles.
Being able to pick up a glass, cup or bottle by the rim and the angle where the side and the base join—using only your fingertips— and pour the contents into another container takes a lot of practice (see Figure 2-2). But that is the only way to do it. After that, the glass or cup must completely air dry before fingerprinting begins. (No, you should not use a hair dryer on it. The resultant heat and rapid moisture evaporation could harm any remaining fingerprints.) This in turn means that very often it must be transported into the police station with the dregs of the liquid still in it—which means that it must be packaged and transported right side up.
For collecting some evidence, -there are special kits you can
buy from suppliers or, sometimes, obtain from the crime lab. To collect blood samples in the preservative jar, simply unscrew the lid, collect the sample with the enclosed eyedropper, and screw the lid down again. The directions that come with the kit tell you which items do and do not need to be refrigerated. (After we got a refrigerator in the lab, many a day Doc, Butch and I stored our lunches in the same refrigerator that might be containing biological samples waiting to be transported to the lab. We were, of course, careful that everything—including lunches and samples—was properly packaged.)
A rape kit has to be kept refrigerated after use, and it should be transported to the lab as soon as possible. The officer or evidence technician does not personally use the rape kit; rather, s/he takes it to the hospital and turns it over to the examining physician, who will use the kit. (Preferably, the examination will be performed in the presence of a female officer, to cut down on the chain of evidence, unless the officer's presence is too distressing to the victim.) Following the examination, the physician turns the kit back over to the officer. The rape kit contains fine-toothed combs, tapes and vials to collect swabs from several pubic areas, vaginal washings and combings, and loose hairs that might be those of the suspect. These critical bits of evidence are the reason police ask the victim not to bathe until after she has been medically examined; very often the victim will then shower right in the hospital before putting on the fresh clothes she has taken with her. All the clothing she was wearing at the time of the assault and immediately after it will be turned over to the police in hopes that some hair, fiber and/or semen from the assailant remains on it.
Shoe Prints, Tire Tracks
Shoe prints and tire tracks are first photographed with a special camera on a frame that points directly down. Because the camera is on a frame, the ratio of the negative to the original (that is, the relationship in terms of size) is known, and the original track can be exactly reproduced in size. After that, the officer should make casts, often called moulages, of them. S/he begins by spraying the surface with a fixative; ordinary hair spray or shellac will do in a pinch, but a special