Advances in Fingerprint Technology.pdf

Notes: Dissolve the MoS 2 in the distilled water. Add 3 drops of the Photo Flo 200 and
shake the solution well to ensure that the molybdenum disulfide has gone into
solution. This solution has a shelf life of about 6 to 8 weeks.
Spraying Procedure:
1. Shake the reagent solution thoroughly and fill a spray bottle with it.
2. Spray the SPR onto the area to be searched for latent prints. Shake the
bottle between sprayings to prevent the molybdenum disulfide from
settling to the bottom.
3. Using a separate spray bottle with clean water, rinse the searched area
to remove the excess SPR reagent.
Dipping Procedure:
1. Mix the reagent solution thoroughly and fill a photographic processing
tray with it.
2. Rock to mix the solution thoroughly, and immerse the evidence item
in it. Particles of MoS 2 will settle on the surfaces where latent prints
are likely to be located.
3. Repeat the treatment with the other side of the evidence item.
4. After 2 min, carefully remove the evidence item and rinse gently with
clean water.
The developed latent print appears as a dark to light gray color. The SPR
solution has been successfully used to develop latent prints on paper, cardboard,
metal, rusty metal, rocks, concrete, plastic, vinyl, wood, and glass.
Similarly, latent prints have been developed on sticky surfaces, such as soda
cans and candy wrappers. SPR reagent-developed latent prints can be lifted
with clean lifting tape.
Margot and Lennard found that the crystalline structure of the MoS 2
used in the recipe can have a significant effect on latent print development
results. 9 They recommended using ROCOL AS powder, made up as 10 g
with 0.8 mL Tergitol 7 in a 100-mL stock solution. This stock is then diluted
1:10 for dipping and 1:7 for spraying. They further noted that substituting
iron oxide as the powder component, as suggested by Haque et al., 33 proved
less effective in their experience than the molybdenum disulfide.
Ishizawa and collaborators reported testing both white and black suspended
particle mixtures in several “fixer” solutions. 34 The white particle
mixture consisted of 80% agalmatolite, 10% lithopone, and 10% zinc oxide,
all w/v in the fixer. Black particle mixture was 45% carbon black and 55%