Powdering

Fingerprint powders are supplied in field kits in several colors, but black, gray, and dragon's blood are the most frequently used. The commercial powders have been developed over many years. They are dependable and of the proper composition. Choosing the powder that best contrasts with the background is a good rule of thumb to follow. Dragon's blood has the advantage of showing up on either a dark or light background. However, the choice of powder depends upon the objective of the investigator-whether the latent print is being developed for photographing or lifting. A test should be made of the area selected for the test print. First, it should be lightly brushed with powder to see if any unseen latent fingerprint is actually present. Then the surface can be wiped clean and the test print made and processed

Fingerprint powder can be applied with fiberglass, camel hair, and feather brushes.

A large piece of cotton can be used for developing latent prints over a large area.

Several law enforcement agencies have adopted a procedure for lifting latent prints by using an extremely fine metallic powder and magnetic wand. The unit is called a Magna Brush although no bristles are present.

The magnet picks up the powder, and only the powder touches the latent print, reducing the possibility of destroying ridge detail as is possible with a bristle brush. Excellent prints have been developed on wood leather, paper, and even cleansing tissue by using the Magna Brush. However, the Magna Brush process is comparatively expensive, and good results can be obtained with the normal techniques and equipment.

With ordinary fingerprint powders a technique that has been very satisfactory for developing latents on paper, especially if the prints are fresh and the paper only semiglazed, is to allow the powder to slide back and forth over the paper without brushing. Brushing has a tendency to disturb the fibers of the paper and destroy detail.

The key to successful powder development is to use a small amount of powder with a delicate touch.

A portion of the powder should be poured out of the container onto a sheet of paper. The ends of the brush bristles should be just touched into the powder. Then the excess powder should be shaken off.

A smooth stroke, using the fingers to guide the brush over the suspected area or over the barely visible print, is the technique to adopt. When sufficient ridge detail has been developed so that the direction of flow of the ridges can be observed, the brushing, if continued, should follow the ridge flow. When the ridge detail has been developed it should be photographed.

After the print has been photographed if desirable, the powdering can be continued to bring the print up into ^{greater visibility.} It may then be advisable to photograph it again.

Occasionally, in spite of all precautions, the powder will adhere so tenaciously to the object on which the latent is found that brushing will not remove the excess powder. If so, the first lift is used to remove the excess powder and the second to preserve the fingerprint for identification purposes. Sometimes a latent print may be improved after the initial lifting by additional processing with brush and powder.

Partial prints should be marked for orientation. For example: Which is the tip end? From its location and if other fingerprints or fingermarks are present, it may be possible to determine which finger of which hand made the latent.

If two or three prints are available, it is nearly always possible to determine which fingers made them.

Fingerprint equipment may include fluorescent powders for developing latent prints on multicolored surfaces, but these powders are not normally a component of issued kits. A source of ultraviolet light is required. Synthetic powders are the best fluorescent powders, but natural minerals can be used. Only long-wave ultraviolet light should be used; a short-wave ultraviolet light is harmful to the eyes and skin. If short-wave ultraviolet is used the investigator should wear protective goggles and clothing. Inasmuch as latent prints are normally lifted the use of ultraviolet powders is infrequent.

Nonflammable objects may be passed through smoke of a burning piece of pine wood. A black, even deposit of soot will form on the object, and careful brushing will often result in developing old latent prints.

This procedure may also be used to acquire a small supply of black powder when in the field without proper powders. By removing the accumulated smoke particles from time to time, sufficient powder maybe obtained to process latent prints. This process should be used for developing latent prints after attempts with brush and powder have failed.

Lifting Fingerprints

The most common materials used for lifting latent fingerprints are rubber lifters and transparent lifting tapes.

Rubber lifters store well and come in both black and white for use with different colored powders. A lifter large enough to cover the print, while leaving plenty of room, should be used. The plastic cover should be carefully removed in one steady movement since any pause will result in a line being left on the tape. In most cases, the powder on the print will not stick to the line, possibly ruining the print.

Apply the adhesive side of the tape to the powdered print, press it down evenly, and then peel the tape from the surface in one smooth, even motion. Replace the plastic cover on the tape over the lifted print to protect it. Rubber tape is better than transparent lifting tape for taking prints from curved or uneven surfaces.

Transparent lifting tape has the advantage of presenting the lifted fingerprints in the correct position rather than reversed as on the rubber tape. The tape is available in dispensers, which speed up the lifting process. Prints on transparent lifting tape should be mounted on material with a color contrasting with that of the lifting powder.

When lifting a print with either transparent or rubber lifters, care should be taken to preclude the formation of air bubbles under the lifter. Keeping a quarter twist on the tape with one hand while rolling it flat with the other will help prevent air bubbles.

Latents found in dust should first be photographed, then lifted. They should not be powdered, as that would destroy them.

Ordinary transparent tapes used in the home or office are not really suitable for lifting fingerprints; however, they may be used as a field expedient. Other available lifting materials are white and black opaque lifting tapes, which are applied like rubber lifters. There are also hinged lifters with transparent tape and white and black backings, which are used in the same manner as lifting tape.