Actual trends in the use of the kastle-meyer test: applications in different species and verification of the limit of detection of sensitivity and vestigiality

Abstract

Forensic Science is formed by areas that perform analysis in different traces found in crime scenes and that can correlate with the fact that happened, thus being able to help in judicial procedure. One of the most important evidence found at a crime scene is blood, but to prove it, rapid tests are performed, such as the Kastle-Meyer (KM) test, which is widely used nowadays because it is considered a fast, cheap and efficient test. Its principle is based on the decomposition of hydrogen peroxide by the hemoglobin present in the blood in water and oxygen, changing the color of the substrate, along with the presence of phenolphthalein, from colorless to pink. This test is well characterized in human blood, but there are no reports referring to its efficiency in blood from animals of other species, which is of extreme relevance, since there are differences in relation to hemoglobin of different species and, still, the number of reports against animal abuse have grown in last years. Thus, the objective of this study was to evaluate the efficiency, sensitivity and vestigiality of the Kastle-Meyer test in human, dog and cat blood. The results showed that, since the three species studied were mammals, the test was efficient in detecting the presence of blood, as well as, in relation to sensitivity, for human and canine blood the test was able to detect to be blood until the dilution of 1:10.000, while for cats the reagent showed positive results up to the dilution of 1:1.000. In relation to the vestigiality, different products such as water, sanitary water, 70º alcohol, anionic surfactant and quaternary ammonia were used to clean the blood and then the reagent was tested, which presented positive results for the three species used. Thus, it is possible to conclude that the KM reagent is an important spot test that can be used in crime scenes both to detect the presence of human blood, and for domestic animals such as dogs and cats. In addition, in the case of an unpreserved area, the test was also shown to be effective in providing positive results for different blood dilutions and for latent blood.