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Chemical Enhancement of Fingerprints in Blood - Coggle Diagram
Chemical Enhancement of Fingerprints in Blood
Blood
commonly encountered as a transfer medium for fingerprints at crime scenes
residue may retain enough color to allow it to be photographed directly
more often, the residue is so faint that ordinary light photography is ineffective
chemical methods for the enhancement of residual blood have been successfully used for years
leucomalachite green
chemically react with components in blood to form a dark-colored dye complex and have all been successfully on light-colored or transparent surfaces
have low background colors but are unsuitable for non-porous surfaces as they run off, and either distort the print or fail to react before detail can be photographed
amido black
is very sensitive and works well on non-porous surfaces but its high background color (light to medium blue) compromises contrast on porous surfaces from which the stain cannot be removed by rinsing
ninhydrin
on dark surfaces, none of these color-producing reagent stains could be guaranteed to produce detectable prints
Experiment
bloodstains were prepared by adding 30 ml of whole, human blood to clean cotton swabs
the stains were allowed to dry for 24 hours at room temperature and two bloodstained swabs were each dipped into one of the following reagents:
merbromin
amido black
fluorescin
LCV
DFO
ninhydrin reagents
Results
all 12 treated bloodstains (each duplicate sets of stains treated with a different reagent) were successfully typed in all 14 loci
the types were readily interpretable and the same types were obtained with the treated and untreated bloodstains
the typing profiles obtained with the treated bloodstains were comparable to the typing profiles of the untreated bloodstains
the only noticeable differences between the treated and untreated bloodstains involved the bloodstains dipped in the merbromin and ninhydrin reagents
the differences observed were:
a faint product band for the DQA1 locus for the ninhydrin treated bloodstains
the larger loci in the AmpFLSTRO Green! and AmpFLSTRO Blue showed a minor reduction in signal intensity
Chemical Hazard Information
"it is important to note that many chemicals, especially a good percentage of those used in forensics, have not been thoroughly (sometimes even minimally) investigated for their toxicological effects or other health and safety impacts"
in some cases, inferences may be drawn from anectodal or associated literature regarding potential health and safety impacts