General Study Guide - Ontario Police College

3. Modified Physical Developer (MMD) (Porous & non-porous
surfaces.)
New procedure reported in 1989 involving treating the item with
a colloidal gold sol’n and then a weak (modified) Ag-PD sol’n.
This technique was called “multimetal deposition” (MMD)
Works well with many surfaces and materials such as floppy disks,
adhesive tapes, metals, papers, Styrofoam, credit cards and glass.
It can also be used for specimens that have already been treated
with ninhydrin. (AF.T. pg. 138-140; pg.262-266)
Colloidal gold particles (in a sol’n pH ~3) are highly
negatively charged & thus bind to amino acids, peptides
and proteins in fingerprint residue. The bound colloidal
gold provides a nucleation site around which silver
precipitates in the second incubation step. (“One speaks
of silver amplifying the gold image. A.F.T. pg.263)
4. Sudan Black
A dye stain technique for use on non-porous wet items.
It is considered less sensitive than other wet item techniques in
use.
Sudan black is considered useful for those wetted items whose
surfaces are contaminated with substances such as grease,
beverages and food-stuffs.
May be used as a post-cyanoacrylate developer, and is especially
useful for post-cyanoacrylate staining on the inside of latex
gloves.
Dark Blue
Dark blue-stained ridge detail is revealed upon a tap
water rinse and the item allowed to air-dry.
5. Oil Red O
A lipid-specific dye stain technique for use on porous items which
have become wet. Research has shown that Oil Red O can be
superior to Physical Developer to develop latent fingerprints on
thermal paper and standard white paper. Fewer immersion steps
and less need to avoid chloride contamination are benefits using
the Oil Red O reagent.
Red
Sensitive to lipid components.
Visible chemical/stain reaction.
Image enhancement methods can be used to improve the
contrast between the stained ridge detail and the pink
background.