Esterase D typing of bloodstains by non-equilibrium focusing.

Non-equilibrium focusing in a pH 4-6 gradient in ultra-thin polyacrylamide gels has been shown to be a reliable and reproducible method for detecting the six common esterase D phenotypes (EsD 1,2-1,2,5-1,5-2 and 5) in dried bloodstains. Successful typing is dependent on both the age and phenotype of the stain in question. The effects of age on the isozyme pattern of each phenotype are described and illustrated. In a comparative trial using 100 simulated and 300 authentic casework bloodstains, non-equilibrium focusing was shown to be more efficient than thin-layer starch gel electrophoresis for the typing of esterase D.