Abstract
Humans and great apes do not possess urate oxidase (uricase); hence, uric acid (UA) is the main end product of purine metabolism in these species. Based on the facts described above, the uricase method utilizing the decrease rate of absorbance at a maximum of 293nm for UA has been widely used in the forensic laboratory. However, Dalmatians excrete a large amount of UA because the reuptake of UA in urinary tubules is disturbed. Fecal stains of birds usually contain a large amount of UA since it is their final product of protein metabolism. Therefore, the uricase method may not be reliable for identification of human urinary stains. We have reported a practical method for identification of human urinary stains by the UA/urea nitrogen (UN) quotient; UN was chosen as an indicator of concentration of urinary components because it is the universal end product of protein metabolism in all mammals. In this study, our method was compared with the uricase method by analyzing urinary stains obtained from 60 different humans, 14 species of non-human primates, 11 species of mammals and 31 different kinds of dogs along with fecal stains from 6 different birds. With the uricase method, urinary stains obtained from three kinds of dogs including Dalmatians, chimpanzees, tufted capuchin monkeys, cotton-headed tamarins, guinea pigs and cattle as well as fecal stains of birds could not be differentiated from human urinary stains. Conversely, not only urinary stains from all mammals except for Dalmatians and chimpanzees but also fecal stains of birds could be differentiated from human urinary stains with our method. From the results obtained, our quotient UA/UN method was proved to be useful in forensic science practice.
