Fingerprint Recovery in the Wet… It's not possible, is it?
“Sorry Madam, we will never get fingerprints from that. It’s raining you see and they will be washed away…”
As usual that statement is quite untrue. You may or may not get fingerprints from the item but you will never know if you don’t try.
There are several products you can use to recover these prints and I have skimmed over the actual method(s) just to give you an insight.
Small Particle Reagent (SPR) is a suspension of finely ground particles in water with a detergent solution. It is used in the enhancement and recovery of fingerprints from non-porous surfaces that have been or still are wet. This technique can be applied in the rain (although not if it is too heavy).
The grey, shiny prints that are developed with SPR can be lifted (after drying) with gelatine lifters, instant lifters or tape, or photographed.
There are two methods of application one known as the Dish Application Method and one as the Spray Method.
Practitioners have their own preferred method of application but I believe it matters not and the size and type of evidence determines what application method you use.
Smaller items that are able to be returned to the laboratory can be subjected to the Dish Method which is similar to the method used with Physical Developer of submersion followed by rinsing with sterile water.
Larger items or those that are non-removable will need to be subjected to treatment at the scene. This method can also be used in the rain and involves spraying the suspension on the item and then using rinse bottle to gently wash the area where you suspect the latent prints.
The flake within the suspension sticks to the fingerprint via the sebaceous fats excreted from the body. The rinse will wash gently over the print, and all waste flakes will wash away. This treatment must be carried out gently or the evidence will get washed away.