Chapter 16

_The Use of the Fingerprint Camera_

If a fingerprint is visible, an effort should be made to photograph it before any attempt is made to develop it. In every case a print developed with powder should be photographed before lifting. It sometimes happens that the print does not lift properly although it may be quite clear after development.

The camera which is especially adapted to the purpose and which is easiest to handle and operate is the fingerprint camera, one type of which is shown in figure 424. This camera has several advantages in photographing fingerprints:

It photographs the prints in natural size. It contains its own light source. It has a fixed focus.

Cameras of this type are available in models operated by batteries and 110-volt current. It is believed that the battery-operated type has the greater utility, since house current may not be available at the crime scene. When not in use the batteries should be removed as they will eventually deteriorate and corrode the brass contacts in the camera.

The camera is of the box type and has three button controls which will open: (1) The metal flap covering the aperture, (2) the front portion of the frame providing access to the self-contained light bulbs, and (3) the camera in half, providing access to the batteries and the shutter as shown below in figure 425.

A 2-1/4 x 3-1/4 film pack adapter or a 2-1/4 x 3-1/4 cut film holder holds the film in the camera. The film pack adapter will hold a pack of 12 sheets of film, and accordingly, will permit the taking of 12 pictures. The cut film holder is a unit which holds two sheets of film utilizing each side of the holder.

It is pointed out that the FBI uses the film pack exclusively in view of the fact that practically all latent examinations will necessitate the taking of more than two pictures. Further, the film pack is made so that it may be loaded into the adapter in the open light. Also, the films are numbered 1 through 12, which is a valuable feature in that in maintaining notes concerning the latent examinations it is a simple matter to note by the number of the negative where the latent impression was developed and photographed. Should it happen that during a latent examination all twelve of the films are not used, the film pack, with the slide in place, is taken into the darkroom and only those films which have been exposed are removed and developed. The unexposed films remain in the film pack adapter with the slide in and may be used later.

As was previously mentioned, the camera has a fixed focus; that is, the camera will take a legible picture only when the latent print is at the focal point, or exactly flush with the opening of the camera. The latent print must not be inside the open end of the camera, nor must it be beyond; otherwise, the picture will be blurred.

Since the camera has its own light source, any leakage of outside light will cause overexposure of the film. Consequently, if the surface of the object bearing the latent print which is to be photographed is uneven or does not cover the entire front of the camera opening, it will be necessary to use some opaque material such as a focusing cloth or heavy dark material to cover the front of the camera so as to exclude all outside light (fig. 426). If a latent print on a pane of glass or an automobile window is being photographed, it will be necessary to back up the latent so that there will be no light leakage. Material showing a pattern or grain should not be used for this purpose as any such pattern will photograph in the background and possibly obliterate the ridges of the latent print.

To insure an equal distribution of the light over the latents being photographed, the impressions should be centered in the opening of the camera. This is accomplished by opening the angular front section of the camera after the metal plate covering the front has been opened, and setting the aperture over the latent impressions so that they will be as near the center as possible. Then, holding the camera firmly in place, it is carefully closed (fig. 427).

During exposure the camera must be held perfectly still. Any movement of the camera or object will result in a fuzzy or double image.

In photographing a small, movable object such as a bottle or tumbler, the camera should not be placed on its end and an attempt made to balance the object across the opening. Instead, the camera should be placed on its side and the bottle or tumbler built up to the opening so that there is no necessity for holding the object (fig. 428). There will be, of course, instances where the camera will have to be held, such as to the side of a wall, cabinet or automobile. Here an extreme effort should be made to avoid moving the camera or permitting it to slip during exposure.

Anticipating the possible use of the photographic negatives in a court proceeding, it becomes of paramount importance to be able to identify them. This is done by using what is called an identification tag. The tag consists of a small piece of paper bearing the date, initials of the examiner, and possibly a case number, and it should be hand-written. The tag is placed near the latent prints being photographed so that it will appear in the picture. It should be borne in mind that concentration should be on the latent impressions, which must be centered, and the identification tag should be to one side and not covering any of the latent prints. Another method of identification, if the surface permits, is to write the above-mentioned data on the surface of the object bearing the latents so that the information set out will also be a part of the picture. Too much emphasis cannot be placed on the importance of the identification tag. The lack of such data, by discretion of the court, may exclude the latents as evidence, in the absence of the original specimen bearing the latents.

The following are suggested exposure times for Tri-X film (available in 2-1/4" x 3-1/4" film packs) with battery-operated cameras having lenses without diaphragms:

Black powder print on white or light background--snapshot Gray or white powder print on black or dark background--1 second

These same exposure times can be used on some cameras having lenses with diaphragms, provided the lens opening is set at f6.3.

The above exposure times are for cameras with batteries in average condition. If batteries become weak the exposures may be increased slightly.

In making snapshots the shutter mechanism should be manipulated as rapidly as possible since slow motion will appreciably lengthen the exposure. In making time exposures the camera shutter must be held open for the desired time. Personnel with photographic experience may desire to use cut film with the fingerprint camera. A few tests will determine the optimum exposure times for any particular type of film.

Briefly, the procedure for taking photographs of latents is as follows: The film pack is placed into the film pack adapter with the safety paper side of the film pack to the slide side of the adapter, care being taken to see that all of the paper tabs are outside of the adapter. The adapter is placed on the camera in its proper position by opening a slide clamp attached to the camera, fitting the side of the adapter into the slot away from the clamp and pushing it down flat into the opening. Don't try to slide the adapter into the opening from the top. The adapter is locked in position by closing the clamp. Next the slide is removed and the tab marked "Safety Cover" pulled out as far as it will come and torn off. The camera is placed in position and the first exposure made; then the tab marked "1" is pulled and the next film is in position for exposure. This procedure is followed with each succeeding film until all have been exposed.

When the last tab has been pulled out, the pack can be removed from the adapter in daylight. If all of the films have not been exposed the slide is replaced into the adapter and the film pack removed from it in a darkroom, as previously stated.

As a matter of regular policy, it is recommended that more than one exposure be made of each latent, varying the normal exposure time to insure satisfactory results, especially when the contrast is not a good black on white or gray on black.

Before starting to photograph, note the following:

- Check shutter action.

- Check bulbs, batteries, and lights.

- Center latents in opening of camera.

- Latent being photographed must be flush with opening of camera.

- Outside light must be excluded.

- Include identification tag in photograph.

- Remove slide and pull safety tab of film pack before making exposure.

- Hold camera still while making exposure.

- Pull correct number tab after each exposure (be careful not to pull more than one).

- Do not use grained or uneven material as a backing when photographing latents on transparent glass.

- Mirrors, polished chrome, and nickel plate will photograph black in the fingerprint camera.

The foregoing has dealt with the standard use of the fingerprint camera when the direct light afforded by the camera gives suitable results. There will be cases, however, where the results from the use of the direct light may not be adequate. Such cases may involve molded or embedded prints, such as prints in putty, wax, soap, etc. Should direct light give poor results, side lighting may prove effective. This can be done by loosening two of the bulbs on one side so that they will not light. The light given by the other two bulbs is directed so as to pass at right angles, as much as possible, across the ridges of the embedded latent print. Adjustment of the exposure time must be made when this is done.