Occult bloodstains detection in crime scene analysis

Abstract

Blood detection in forensic investigation is the milestone in crime scene analysis. Locating bloodstains on dark clothing are often difficult and it is well known the discrepancy about selection of the most suitable method to locate and identify blood stains, depending on the presence of different contaminants and the occurrence of false positives or negatives of human’s blood. The main purpose of this paper was to compare different orientation tests for blood detection on different materials, presenting with contaminated samples and treatments. Human blood was tested in car mat, dark tiles, unlacquered wood surface and sneakers with recent and old stains. Samples were prepared with blood, paint, bleach, dish soap multi-use cleaner, juice, fruit and milk using different combinations and protocols. In the case of forensic lights, and depending on the wavelength and filter used, latent stains were not detected and some false negatives and false positives appeared in different contaminants and treatments. In addition, bleach resulted the main contaminant, altering most tests. In conclusion, our results confirmed that luminol is the most effective test for detecting fresh and latent blood stains, because no type of contamination interfered on its reliability.