Fluorescein As A Suitable Replacement
for Luminol As A Latent Blood Detection System
(The following topic was presented at the February 4, 1995 SCAFO meeting with slides and video tape illustrating the methodology and results.)
Speaker ROB CHEESEMAN, Microbiologist
Balboa Naval Hospital
During the 1980's, the Environmental Protection Agency (EPA) became more strict with respect to toxic and/or mutagenic reagents utilized in the workplace. Many reagents used cavalierly in the past were placed under greater scrutiny resulting in the enforcement of more stringent safety guidelines. Luminol has been erroneously listed as banned for use in California in some literature. The current MSDS lists both luminol and fluorescein as �possible carcinogenic�, hence no such ban is in place on these reagents at this time. Fluorescein has a twenty year history in the medical field of ophthamology and is Food and Drug Administration (FDA) approved for clinical application in retinal and choroidal angiography.
The 1991 Maucieri and Monk (California Criminalistics Institute) study listed fluorescein as the reagent with the greatest promise to replace luminol in the detection of latent bloodstains. Like luminol, fluorescein is a technique in which latent blood stains can be made temporarily visible (luminescent) by application of the fluorescein. Unlike luminol's single reagent application, fluorescein requires an application of itself followed by hydrogen peroxide (H2 02). This double reagent application can be problematic, especially on vertical, non--porous surfaces. A commercial thickener was used to overcome this problem, affording crime scene photographers greater opportunity to document the bloodstain patterns as evidence.
The fluorescein reaction can be documented with still photography or by video camcorder. The scene should be photographed prior to the fluorescein application. Examine the substrate with the suspected bloodstain for any native fluorescence and document the results by photography. Test the fluorescein reagent on sample blood and check for a reaction. Apply the reagent on a like substrate, check for cross reaction, and document the results. The reaction can be visualized and photographed with and without the use of an orange barrier filter. Unlike Luminol photography, the scene does not need to be completely darkened for the reaction to be visualized. Some ambient light in the scene aids the photographer/investigator in orienting the scene and its contents, and alleviates the need for fill flash.
Photographic documentation of the fluorescein reaction is best accomplished with a tripod--stationed 35mm camera with the aperture set at F/8 using an orange filter and color print film (EI400). Vary the exposure times, bracketing between 5 seconds and 25 seconds, depending upon the lighting conditions at the scene. Photographs may also be taken utilizing the aperture--priority automatic function of the camera, resulting in quality photographs.
The Fluorescein reaction will continue several minutes before the bloodstain pattern begins to degrade. This allows ample time for the photographer to vary his exposures and document the scene with and without the orange barrier filter.
(Editor--�Mr. Cheeseman is preparing a detailed paper for publication in the near future.)
This article was originally published in �THE PRINT�
Volume 11(2), March/April 1995, pg 3
and has been obtained from the online library provided by the
Southern California Association of Fingerprint Officers