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Fingerprints

The search for latent prints is done in a systematic andintelligent manner. Investigators develop techniques to locatetraces of fingerprints at a crime scene. The basic premise insearching for latent prints is to examine more carefully thoseareas, which would most likely be touched by persons who havebeen on the scene. The natural manner in which a person woulduse and place his hands in making an entrance or exit from abuilding or in handling any object is the key to the discovery oflatent prints.

Where a forced entrance has been made, latent prints are likely to be found on any surfaceadjacent to or at that point. Any object with a smooth, non-porous surface is likely to retain latentprints if touched. Fingerprints on rough surfaces are usually of little value. If the fingermark doesnot disclose ridge detail when viewed under a reading glass, the chances are that its value inidentification is nil when photographed. Where fingermarks are found, it will be necessary for theinvestigator to compare them against the ones of persons having legitimate access to the premisesso that the traces might be eliminated as having evidentiary value if they prove to be from thesepersons. Places to search for prints on an automobile are the rear view mirror, steering wheel hub,steering column, windshield dashboard and the like.

Dusting of surface may be done with a fine brush or with an atomizer. The whit powders usedare basically finely powdered white lead, talc, or chalk. Another light powder is basically Chemist’sgray. A good black powder is composed of lampblack, graphite, and powdered acacia. Dragon’sblood is good powder for white surface and can be fixed on paper by heating. In developing latentprints, the accepted method is to use the powder sparingly and brush lightly. Do not use powder ifthe fingermark is visible under oblique lighting. It can be photographed. A good policy for thenovice is to experiment with his own prints on a surface similar to the one he wishes to search inorder to determine the powder best suited to the surface. Fingerprints after dusting may be liftedby using fresh cellulose tape or commercially prepared material especially designed to lift andtransfer dusted latent fingerprints.

In addition to latent prints, the investigator must not overlook the possibility of two other typesof fingerprint traces: molded impression and visible impression. Molded impressions are formed bythe pressure of the finger upon comparatively soft, pliable, or plastic surfaces producing an actualmold of the fingerprint pattern. These can be recorded by photograph without treating thesurface, is usually most effective in revealing the impressions clearly. Visible impressions are formedwhen the finger is covered with some substance which is transferred to the surface contacted.Fingers smeared with blood, grease, dirt, paint, and the like will leave a visible impression. If theseimpressions are clear and sharp, they are photographed under light without ant treatment.Ordinarily, prints of this type are blurred or smeared and do not contain enough detail foridentification by comparison. However, they can not be overlooked or brushed aside without firstbeing examined carefully.

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专业八级英语考试阅读经典素材汇总