By Pat A. Wertheim
Even though magnetic powder has been available since the early 1960’s, many latent print examiners and crime scene technicians are still not using it to full advantage. Magnetic powder adds a wide range of flexibility to one’s resources. In general, magnetic powder is used on non-magnetic surfaces, and regular powder on iron-based surfaces. However, regular fingerprint powder is inappropriate for some surfaces, including many plastics and textured surfaces, where magnetic powder develops latent prints very well. Textured surfaces such as vinyl imitation-leather or lightly textured automobile dashboards or door panels often respond well to magnetic powder, where regular powder would pack into the low places in the texturing and make development of a good latent impossible. In addition, using the “hot breath” technique, also known as “huffing” works better with magnetic powder than with regular powder.
With magnetic powder, there is no brush with fibers to touch and possibly damage the print. The powder is not itself magnetic, but is attracted by a magnet and carried as whiskers by a magnetic wand. Nothing but the powder itself touches the print. The wand is a closed, hollow tube containing a magnet on a rod. When the rod is pushed in, the magnet is located at the end of the tube and the powder clings to that end. When the rod is pulled out, the magnet is moved to the center of the tube and the powder falls off. With the rod in and a cluster of powder whiskers on the end, you are ready to dust for latent prints.
With regular powder, the more you pass back and forth over the print, the more powder you add to the latent. The opposite is often true of magnetic powder. The first sweep across a surface usually yields as dark a print as you will get. Going back and forth repeatedly will lighten and eventually erase a latent. Therefor, normally, one would stop dusting as soon as a latent appears. However, this characteristic can sometimes be used to advantage. For example, a heavy, greasy print may show up initially as a solid patch, but repeated passes with the wand may actually remove powder from the furrows and yield an identifiable print. This is especially true of greasy prints on car bodies.
Another advantage of magnetic powder is the way in which it lends itself to use with “hot breath.” This technique is necessary in dry, desert climates, but may not be needed often in humid areas. When confronted with a “dead print,” that is, one from which all of the moisture and oil has evaporate, the print can be temporarily re-humidified by “huffing” breath on it from approximately six inches, then sweeping across it with the magnetic powder before the moisture can completely evaporate. Sweeping across the area too soon can result in a general coating of powder, and the resultant destruction of any latent prints. Likewise, waiting too long can result in complete evaporation of the moisture and no print development. A little practice, however, allows one to effectively use this technique. From day to day and surface to surface, slight modification must be made in the time delay between huffing and dusting, but one learns to modify one’s approach quickly as conditions change. The “hot breath” technique is especially useful on plastic bags and similar plastics, and should be tried on any surface where regular powder fails to develop any prints.
In general, magnetic powder is not recommended for surfaces which are themselves attracted to the magnet. However, occasionally magnetic powder will yield a cleaner, crisper print than regular powder. Excess powder may be removed by lightly tapping the object against another surface to dislodge the magnetic particles. Magnetic powder and the “hot breath” technique may also be very productive on a vehicle body following dusting with regular powder. Process the vehicle as usual with regular powder and photograph and lift all latent prints of value. Then reprocess the vehicle in critical areas such as those below the door windows or the roof above the doors, using hot breath and magnetic powder. Frequently, more prints will develop with the magnetic powder than with the regular. Be sure and gently blow off excess powder before photographing or lifting your latent prints.