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CHEMICAL ENHANCEMENT OF FINGERPRINTS IN BLOOD: AN EVALUATION OF METHODS,…
CHEMICAL ENHANCEMENT OF FINGERPRINTS IN BLOOD: AN EVALUATION OF METHODS, EFFECTS ON DNA, AND ASSESSMENT OF CHEMICAL HAZARDS
http://www.latent-prints.com/cac_blood.htm#Safety
accessed: May 5, 2020
Introduction
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either residue retains enough color to allow it to be photographed or
residue is so faint that its color photography is ineffective except on transparent or highly reflective sources
Effective Method:
chemical methods for the enhancement of residual blood fingerprints
- Leucomalachite green, amido black, and ninhydrin
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blood bearing "fingerprint" surfaces may also be subjected to DNA analysis, interferences with current DNA methods could be evaluated using known human blood and subjecting it to the harshest chemical exposure from each method.
Experimental
A folded paper towel "touch pad" was dampened with fresh whole human blood (anti-coagulant added, but no preservative) until touching it just produced an even film of blood on the tips of the fingers
Three fingers (index, middle, ring), were touched simultaneously on the touch pad and then immediately touched repeatedly to the target surface.
Test targets were a variety of porous, non-porous and semi-porous surfaces
sequential touches of a surface provides a convenient, reproducible gradient of concentration of the transfer medium
No matter what the medium is: blood, grease, or natural skin oils, each touch removes a percentage of the medium, leaving less on the skin for the next touch (until it is replenished)
Test
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Amido black (AB):
0.2% solution in methanol/glacial acetic acid (9:1)
Methanol/glacial acetic acid (9:1) rinse
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Fluorescin Working Solution: 60ml stock solution + 10ml 2-propanol + 50ml acetone + 50ml xylene + 830ml petroleum ether
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DFO Working Solution: 60ml stock solution + 10ml 2-propanol + 50ml acetone + 50ml xylene + 830ml petroleum ether
Leuco Crystal Violet (LCV):
Dissolve 10gm 5-sulfosalicylic acid (Aldrich 24700-6)
3.7g soldium acetate
1g Leuco crystal violet (Aldrich 21921-5) in 500 ml 3%
hydrogen peroxide
Merbromin:
Stock Solution: 0.45g merbromin in (Aldrich 19959-1) 100ml ethanol, 15ml formic acid, 10g mossy zinc. Reflux until clear and pale in color.
Working Solution A: 10ml stock/30ml acetone
Working Solution B: 10% hydrogen peroxide/acetone (1:9)
Each target was treated according to the best established method for each reagent (or according to recommendations of authors discussing the newer techniques)
Evaluations of the sequential touch targets were repeated at 10 day intervals, up to 40 days after treatment.
Bloodstains were prepared by adding 30ml of whole, human blood (anti-coagulant added, no preservative) to clean cotton swabs
The DNA was extracted from all bloodstains by digestion with Proteinase K, purification with phenol/chloroform and concentration through microfiltration
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Effects on DNA Analysis
All 12 treated bloodstains (each duplicate set of stains treated with a different reagent) were successfully typed in all 14 loci
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.
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he larger loci in the AmpFLSTRÔ GreenI and AmpFLSTRÔ Blue (CSF1PO and FGA, respectively) showed a minor reduction in signal intensity
clear-cut typing results were obtained for all 14 PCR-based markers from the DNA extracted from the bloodstains treated with each of these 6 reagents
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