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Passage Thirty (Fingerprints1) The search for latent prints is done in a systematic3 and intelligent manner. Investigators5 develop techniques to locate traces of fingerprints at a crime scene. The basic premise6 in searching for latent prints is to examine more carefully those areas, which would most likely be touched by persons who have been on the scene. The natural manner in which a person would use and place his hands in making an entrance or exit from a building or in handling any object is the key to the discovery of latent prints. Where a forced entrance has been made, latent prints are likely to be found on any surface adjacent to or at that point. Any object with a smooth, non-porous surface is likely to retain latent prints if touched. Fingerprints on rough surfaces are usually of little value. If the fingermark does not disclose ridge7 detail when viewed under a reading glass, the chances are that its value in identification is nil8 when photographed. Where fingermarks are found, it will be necessary for the investigator4 to compare them against the ones of persons having legitimate9 access to the premises10 so that the traces might be eliminated as having evidentiary value if they prove to be from these persons. Places to search for prints on an automobile11 are the rear view mirror, steering12 wheel hub, steering column, windshield dashboard and the like. Dusting of surface may be done with a fine brush or with an atomizer. The whit13 powders used are basically finely powdered white lead, talc, or chalk. Another light powder is basically Chemist’s gray. A good black powder is composed of lampblack, graphite, and powdered acacia. Dragon’s blood is good powder for white surface and can be fixed14 on paper by heating. In developing latent prints, the accepted method is to use the powder sparingly and brush lightly. Do not use powder if the fingermark is visible under oblique15 lighting16. It can be photographed. A good policy for the novice17 is to experiment with his own prints on a surface similar to the one he wishes to search in order to determine the powder best suited to the surface. Fingerprints after dusting may be lifted by using fresh cellulose tape or commercially prepared material especially designed to lift and transfer dusted latent fingerprints. In addition to latent prints, the investigator must not overlook the possibility of two other types of fingerprint2 traces: molded impression and visible impression. Molded impressions are formed by the pressure of the finger upon comparatively soft, pliable18, or plastic surfaces producing an actual mold of the fingerprint pattern. These can be recorded by photograph without treating the surface, is usually most effective in revealing the impressions clearly. Visible impressions are formed when the finger is covered with some substance which is transferred to the surface contacted. Fingers smeared19 with blood, grease, dirt, paint, and the like will leave a visible impression. If these impressions are clear and sharp, they are photographed under light without ant treatment. Ordinarily, prints of this type are blurred20 or smeared and do not contain enough detail for identification by comparison. However, they can not be overlooked or brushed aside without first being examined carefully. 1. What is the best title for this passage? [A]. Visible impressions. [B]. Moulded impressions. [C]. Fingerprints. [D]. Latent fingerprints. 2. How many fingermarks are mentioned in this passage? [A]. 2. [B]. 3. [C]. 4. [D]. 5. 3. Which type of fingerprints is most likely to retain? [A]. Latent fingerprints. [B]. Visible impressions. [C]. Moulded impressions. [D]. Clear fingerprints. 4. How many ways are there to develop fingerprints? [A]. 2. [B]. 3. [C]. 4. [D]. 5. Vocabulary 1. latent print 潜在指2. 纹 3. premise 前提 4. non-porous 无孔的，5. 不6. 渗透的 7. ridge 脊，8. 隆起部 9. nil 无，10. 零 11. premise 房屋及其附属部件 12. rear view mirror 后视镜 13. steering wheel hub 驾驶盘 14. steering column 转向柱 15. windshield 挡风玻璃 16. dashboard 仪表盘，17. 挡泥板 18. atomizer 喷雾器 点击  收听单词发音
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