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CAE Wand Method

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This method is not as controlled as the chamber method. More care and caution must be exercised. Proper respiratory equipment must be used to prevent contamination. This method is not suggested when processing on a scene. Simply pass the wand over the areas where the suspected fingerprints might be. The prints should quickly develop into a white film on the surface of the item. The fingerprints may then be photographed or further enhanced with the addition of powders. It is suggested that a short period of time (ten to twenty minutes) be allowed to elapse before applying the powder. This will allow the CAE prints to set onto the surface.

Yellow fluorescent powder results on nonporous object

Figure 5.33 Yellow fluorescent powder results on nonporous object.

Iodine Fuming

The two most common methods by which this technique may be utilized are the iodine fuming gun (most common) and the fuming cabinet. Two other less used techniques are iodine dusting and iodine solution. When applied, the iodine is absorbed by the fingerprint secretion, which produces a dark brownish to blackish appearance. It is thought that the iodine reacts with fatty acids and lipids contained in the fingerprint. This technique is used for paper and may be used on human skin. This technique is very corrosive and may pose safety issues when improperly applied. The resulting prints that develop must be photographed as the prints tend to fade over time. Fixatives may be applied to iodine-developed prints to prolong their appearance.

Yellow fluorescent powder results on nonporous object utilizing an alternate light source

Figure 5.34 Yellow fluorescent powder results on nonporous object utilizing an alternate light source.

Fuming Gun

Constructing a fuming gun requires a glass or hard plastic tube with a small rubber hose used as a nozzle applicator. Iodine crystals, glass wool, and calcium chloride are placed into the gun. To activate the iodine, blow into the mouthpiece and move the nozzle or rubber hose over the object where fingerprints are thought to be. The heat from the breath will activate the chemicals. When the fingerprints develop, they should be noted and photographed as soon as possible to prevent the possibility of loss. Upon completion of the technique, the equipment should be cleaned as soon as possible to prevent corrosion.

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