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If you’re lucky, you may arrive at a crime scene and find an ideal situation for processing. Usually, though, scenes are not pristine. You may have anything from an unsecured shed to open fields to swamps and ponds. Weather is often a problem. In this issue, I’ll look at fingerprinting essentials in extreme conditions.If you’re lucky, you may arrive at a crime scene and find an ideal situation for processing. Usually, though, scenes are not pristine. You may have anything from an unsecured shed to open fields to swamps and ponds. Weather is often a problem. In this issue, I’ll look at fingerprinting essentials in extreme conditions.

Extreme Heat
When dealing with extreme weather, you need to be careful or you could lose evidence. High temperatures cause the oil in fingerprints to be more pliable. Heat also interferes with the lifting tape. If you try to process the print the same way you would in moderate temperatures, you’ll ruin the print. Let’s look at ways to process a vehicle in 100ºF heat.

  1.  Get the vehicle out of the heat. Move the vehicle to a garage or under some type of awning or shade to allow it to cool down. If you can’t move the vehicle, wait until the sun is down and the temperature is lower.
  2. Check for visible prints. Dust and/or pollen can accumulate on vehicles, making it easier to see prints. Also use common sense. Where would a suspect most likely have touched the vehicle? When it’s hot, a suspect may drive with the window down, and his hand may touch along the open window frame or on the door below the window. Check door handles and knobs, door edges, the hood, trunk, the roof, the steering wheel, the shifter, radio, console, and dashboard.
  3. Photograph prints. Before you do anything else, photograph all prints you find. No matter how good you are, something can always go wrong. Better to have a record.
  4. Dust the prints. Fingerprints in extreme heat may streak if you use a regular brush. Therefore, you need to be extremely careful. Use a feather fingerprint brush with black powder to dust the prints. Photograph.
  5. Lift the prints. If you use lifting tape on a hot surface, the adhesive and tape will separate, ruining the print. Instead, use white AccuTrans with black powder. Again, be sure to photograph this step.

Extreme Cold
Dealing with extreme cold can be just as challenging as dealing with extreme heat. When the temperature dips below freezing, you have to thaw prints before processing them. This time, let’s consider a vehicle left out in 10ºF.

  1.  Check for visible prints. As noted above, think about where a suspect might touch the vehicle.
  2. Photograph prints. As soon as you can see prints, photograph them. Remember to photograph before you begin processing, and photograph each step along the way.
  3. Warm the surface. Fingerprints need to be above freezing to process. The best option is to move the vehicle indoors and allow the surface to warm up to above freezing. If you can’t move the vehicle, try to heat up the surface. Aim the beam of a Maglite over the print. Maglites put out a lot of light; depending on the conditions, the heat from the flashlight may be enough to warm up the print. Try letting the sun hit the vehicle. If all else fails, wait until the temperature rises above freezing before proceeding.
  4. Process and lift. Once fingerprints are above freezing, process in the normal way.

Wet Conditions
Many people will tell you that you can’t get a latent print from a wet item. Or they’ll say you have to wait for the item to dry. Well, that’s just not true. With the correct product and techniques, you can process and lift wet prints. For this example, let’s consider a vehicle left in the rain.

  1.  Check for visible prints. As noted above, think about where a suspect might touch the vehicle.
  2. Photograph prints. Remember to photograph before you begin processing, and photograph each step along the way.
  3. Process at the scene. When it's raining, don't be too quick to move a vehicle before lifting prints. If you tow the vehicle in the rain, the grit and grime from the wrecker will act like sandpaper, and you’ll lose the prints. Also, if you let the surface dry out, water spots will form and interfere with the quality of the fingerprints. On the other hand, oil and water don’t mix, so the fingerprints will remain intact on a wet vehicle.
  4. Develop prints. You have two options for developing and lifting latent fingerprints from a wet surface: SPR and Wet Print. SPR is a dry powder that you mix with water and Photo Flo. Once you spray the solution on the wet surface, the SPR adheres to the latent fingerprints, allowing you to see them. Because SPR sprays on grey, you may need multiple applications to get a black print. Wet Print is a premixed solution. Spray it on, then rinse with water, and the prints will be right there. You only need to apply Wet Print once; you get a black print the first time.
  5. Lift prints. Put the tape on top of the wet print. Squeegee out the excess water so that the adhesive makes contact with the print. Lift the print. (For more on lifting wet prints, please go to http://www.csigizmos.com/products/latentdevelopment/reagent.html.)

Processing latent fingerprints can be quite challenging in adverse conditions. If you’re not careful, you can easily lose valuable evidence. But if you take the time to learn the best practices for these situations, you’ll be ready.

Dick Warrington is in research and development and a crime scene consultant and training instructor for the Lynn Peavey Company. dwarrington@peaveycorp.com

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