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Techniques have been taught in training classes and passed down through the years. Since we have all been taught these, we've never tried anything else, so we don't know whether it can or cannot be done. Sometimes you just need to ask "Why not?"
If someone tells me it can’t be done, I try to figure out how to do it. I have the tendency to look at things a little differently. In 1994, I was told a stun gun would not work as a dust print lifter; I came up with an idea, tried it, and it worked.
Some of the techniques we have been taught include developing a latent fingerprint on a piece of paper or paper towel. You photograph and cover it with lifting tape for preservation since it can’t be lifted. Another example is that of a textured item, such as a car dash, that is usually not processed because the latent print cannot be lifted. To lift these developed latent prints, use Diff-Lift tape.
If there is a latent print on a feather, it can’t be developed with fingerprint powder and lifted. With proper powder applications and standard lifting tape, the print can be developed and lifted.
Granted, you probably won’t have the occasion to develop and lift latent prints off paper towels or feathers. The bottom line is if you can lift prints off paper towels and feathers, what can’t you process for latent prints?
Let’s say a cold beer can was found at a crime scene with condensation on it. Normally, the condensation has to dry on the can before it can be processed. If you let it air dry, the can gets water spots on it, which, in turn, mess up the latent prints.
If a person touches a surface that is wet, there is a possibility it could transfer the oils from their fingers to the wet surface. Oil and water do not mix. The oily print will transfer to the surface through the water.
Small particle reagent (SPR) can be used to develop latent prints on a wet surface—it is like liquid fingerprint powder. When sprayed on the surface of non-porous wet evidence, the micro-fine particles attach themselves to the latent print residues as the solution runs off the surface. The residue is sprayed with water to remove excess solution and the developed latent fingerprintcan be lifted with standard lifting tape.
We have been told to allow the area and the print to air dry and then lift off the surface. This would be great if time is of no importance and it is not the rainy season because lifting tape will not adhere on a wet surface. This, of course, is wrong. Adhesive is still on the tape but the water is making a barrier between tape and surface. By using a squeegee to remove the water, the tape will adhere to both the surface and the latent print, allowing the processed latent print to be lifted. Developing and lifting latent prints off wet surfaces while still wet gives one more option when processing crime scenes.
Dick Warrington led the Crime Scene Unit for the Shawnee County Sheriff’s Dept and was the lead crime scene officer for the Capital Area Major Case Squad for many years before his retirement in 1996. He is a member of the Kansas I.A.I. and a board member of the International Crime Scene Investigators Association. Dick is the developer of several products used in crime scene investigation. In his retirement, he is in research and development and a crime scene consultant and training instructor for the Lynn Peavey Company. For the past five years, Dick has been teaching classes throughout the U.S. and Canada, trying to dispel some of those “you can’t do that” myths. More myth-busting ideas are available at www.csigizmos.com.