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Presumptive Testing for Blood on a (This article is reprinted from Volume 21 Issue 1/2, Summer/Winter 1997, Tieline, published by the California Department of Justice, Bureau of Forensic Services. Thanks to Bill Corson, N.C.I.S.)
by STEPHEN BENTLEY In certain instances a fingerprint is found to be made in blood, and the preservation of this patent print precludes any presumptive testing for blood. If this is the case, the processing of this print may involve the use of amido black. “Amido black is a dye which stains protein present in blood to give a blue--black product. It will not detect the normal constituents of latent fingerprints...”1 Can amido black be considered a presumptive test for blood? Can this amido black developed print be tested chemically for the presence of blood and then immunologically for the presence of human blood? These questions were addressed by obtaining the amido black reagents, used by the Latent Print Section, and testing various physiological fluids. I made patent prints with my own blood and then developed them with amido black according to the procedure used by the Latent Print Section. This procedure involves “fixing the print” on the object using methanol and then applying the amido black development reagents. The bloody prints became intensely dark blue in color, enhancing even the faintest patents. A developed print was then subjected to a presumptive test for blood by swabbing a portion of the print with a water moistened swab and then conducting the leucomalachite green test. The blue material on the swab lightened slightly and then a color change occurred in which the outer areas of the blue sampled material turned blue--green and the center of the sample material remained blue. A swab with only the amido black reagent was then tested and compared to the stained blood sample. A color difference between the two was apparent. The reagent control swab remained a blue color, somewhat lighter in color. Saliva, semen, and nasal mucous were tested in the same manner as the blood. The dried saliva would not fix to its glass matrix and no material remained for the development step. The dried semen and the nasal mucous remained fixed onto their glass matrices (to a lesser extent than with blood) and developed a light blue to blue color when the Amido Black reagents were applied. Prior to their treatment with amido black, the leucomalachite green test was performed on a portion of the semen and nasal mucous. No color reaction was observed with either sample type. Further, a species determination was performed twice on portions of a developed bloody fingerprint and there was no precipitin reaction to anti--human serum. Amido black will react with other physiological fluids such as nasal mucous and semen but, to a much lesser extent than blood. A patent print in suspected blood, whether it's blood or not, must be able to survive the “fixing process” before developing with amido black. Otherwise, no patent remains for development. The dried blood survives the amido blood staining process with no obvious loss of material. This was not the case for the other dried body fluids. After a fingerprint has been developed with amido black, it is possible to determine whether this print was made in blood by conducting the leucomalachite green test for blood. It is advisable to run an amido black reagent control for comparison purposes. Immunological testing for the presence of human blood was not successful using the Ouchterlony immunodiffusion method. However, DNA testing of this developed print may be a possibility and should be explored. If successful, the question of whether this blood is human or not could be answered (not to mention the possibility of gaining typing information).
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This article was printed in “THE PRINT” |