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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
By DeHaan, Clark, Spear, Oswalt, and Barney from CA Department of Justice, Bureau of Forensic Services in Sacramento, CA
Blood is encountered as a transfer medium.
Ordinary light photography is sometimes ineffective.
Tunable-wavelength light sources allow playing of wavelength for most absorbance in residual hemoglobin.
Chemical enhancements include: Leucomalachite green, amido black, and ninhydrin.
Leucomalachite green and ninhydrin have low background colors and cannot be used for non-porous surfaces.
Amido black works well on non-porous surfaces but has high background color.
In 1995, leuco crystal violet was propsed as a developer on light backgrounds and merbromin for dark backgrounds. (John Neuner). Everse and MEnzel suggest merbromic to develop flurorescing prints on non-porous surfaces.
Bodziak recommended crystal violet for shoeprints in blood while Maucieri and Monk recommended flurosecin as a potential candidate. Cheeseman and DiMeo applied fluorescin to BLOODY fingerprints in a visicous medium that reduced running.
Test targets were porous, nonporous, and semi-porous surfaces.
White typing paper, black construction paper, brown paper bag, bar wood, white contact paper, textured gypsum board painted with latex wall paint, weathered finberglass panel, smooth-surface glass bottles, plastic soft drink bottles, aluminum cran.
Multiple touches were done on each surface target so the concentration of medium would be less and less.
Tests were done 1 day, 10 days, and 30 days after prints were deposited. Targets allowed to dry for 18 hours at RT.
White typing paper also had diluted blood (1:10 and 1:1,000,000) of single drops that were allowed to dry at around 30 degree Celsius for 4 hours.
Reagents for tests:
Ninhydrin, Amido Black, DFO, Fluorescin, Leuco Crystal Violet, Merbromin
Ninhydrin: dip target into solution for 5 x then drain excess. Air dry and develop at RT for 7 days prior to reading.
Amido Black: applied using squeeze bottle then rinsed with cold tap water.
DFO: target immersed (two times) with air drying in between. Heat at 85 degrees C in dry oven and evaluted using 532 nm wavelength.
Leuco Crystal Violet: Fine-mist aerosol in fume hood (developed for 30 seconds) then rinsed with tap water.
Fluorescin: fine-mist aerosol then allowed to dry at RT.
Merbromin: fine-mist aerosol then allowed to dry at RT.
Ninhydrin, LCV, and AB evaluated in normal lighting.
Merbromin, DFO, and fluorescin evaluated in different wavelengths with barrier filters.
DNA Analysis: 30 mL of human blood was applied to cotton swabs then dipped in each reagent. Positive controls were not treated with reagents. Bloodstains then maintained for 11 days at RT then frozen for 20 days. DNA extraction was successful except in merbromic or ninhydrin. A faint band for DQA1 locus in ninhydrin was shown and a larger loci in the AmpFLSTRO GreenI and Amp FLSTRO Blue shows minor reduction in signal intensity. Any significant loss of sample will negatively impact typing results.
Summary:
leuco crystal violet appears to be an efficacious tool for analysis. LCV had some health hazard which may be problematic to LEO and public. LCV is highly to moderately toxic.
Report Findings for testing on surfaces:
http://www.latent-prints.com/cac_blood.htm
Author Recommendations if using LCV:
a. Risk Management including evidentiary worth, forensic value, potential health effects, long term liability.
b. Inform LEO of findings including any liability issues.
c. target substance of LCV should be CLEARLY identified.
d. If LCV cannot be removed, removed area of substrate with LCV from crime scene.
e. Aerosolized LCV should be used sparingly.
f. PPE should be used.
g. all PPE that is contaminated should be bagged and disposed as Hazardous waste.
h. Personal hygiene should be used
i. limit number of individuals using LCV
j. LEO should post hazards at scene.