Identification of human urinary stains by the quotient uric acid/urea nitrogen.

Uric acid (UA) and urea nitrogen (UN) were determined in urinary stains and the UA/UN x 20 values were calculated. The values in human urinary stains were 1.11-4.21, while those in other mammals except some of chimpanzees, were under 0.7, and those in fecal stains of birds were over 80. Most of the stains of other human body fluids or plant juices tested contained neither UA nor UN, and some contained one, but never the other. Ascorbic acid (AS) of up to 100 mg/dl in urine did not interfere with UA determination when dried human urinary stains were analyzed. It was also found that the contents of UA were very low at the peripheral parts of urinary stains. The present results indicate that the quotient UA/UN is useful for identification of human urinary stains in forensic practice provided that the peripheral part of the stain is not used.