This technique may be used in two methods, the fuming chamber (Figure 5.14) or tenting method, or with a wand. CAE reacts with the amino acids and fatty acids in the perspiration to form a white-colored polymer. Contrast may be enhanced through the use of a variety of powders or dye
Figure 5.30 Lifted fingerprints on latent fingerprint card with technician's initials.
stains applied to the developed polymer. Commonly, fluorescent powders and dye stains are applied on surfaces where the contrast is less than desirable. An ALS or laser is then used to enhance the print, after which the print is photographed. This method may be applied to metal, glass, plastic, garbage bags, electrical tape, and many other nonporous surfaces.
Caution: When using the CAE method, caution is paramount. This chemical has the same effect as tear gas and may aggravate the mucous glands and membranes.
Figure 5.31 Florescent powders and alternate light source on nonporous objects (fluorescent powders also come in magnetic form to be used on porous objects). Black latent cards assist in viewing results.
Fuming or Tenting Method
Place the specimen, preferably suspended, into a fuming chamber. This allows for the vapors to evenly adhere to the surface(s) of the items. Place ten to twelve drops of liquid CAE into a pipette or aluminum dish that is sitting atop a hotplate or heating device. Pleat the CAE, and the vapors should become visible. Where a prepackaged envelope of CAE will be used, simply open the envelope and allow the CAE to disperse into the chamber. Allow the item to remain in the chamber for a minimum of one to two hours. This will allow the CAE to set onto the specimen. To enhance the development process, humidity should be present. Where a chemical reactive process is used, such as sodium hydroxide, place the item to be processed into the chamber. Place cotton treated with sodium hydroxide into an aluminum dish; then add several drops of CAE to the sodium hydroxide-treated cotton. The reaction should be immediate and the vapors will quickly appear. A word of caution, this technique generates a great deal of heat. Some types of hot pad or aluminum should be placed under the cotton to prevent heat damage. To enhance an even dispersal of CAE, a fan should be in the chamber to provide circulation. The fan does not need to be set on high. The purpose is simply to allow the vapors to disperse throughout the chamber. Where there is a large
Figure 5.32 Using yellow fluorescent powder on nonporous object.
chamber to be processed, a room or vehicle, the investigator should take the appropriate action to ensure the least amount of contamination occurs.