Feasibility of Using the Least Square Deconvolution Approach to Resolve Three-Person STR DNA Mixture Samples

The feasibility of using the least-square solution method to resolve three-person mixtures of short tandem repeat deoxyribonucleic acid (STR DNA) was explored in this work. Such three-person mixtures can occur in gang rapes and other violent crimes and there is currently no suitable method for resolving these mixtures. The method evaluated in this work was named LSD-3. Simulations were conducted using the MATLAB software package to evaluate the sensitivity of correct resolution to signal perturbations as a function of the relative mass ratios of the mixture contributors. Three enhancements to the LSD-3 method were investigated; locus concatenation, reference profile incorporation, and manual analysis of allele peak area data guided by LSD-3 mathematical results. It was found that while locus concatenation did not increase the ability of LSD-3 to correctly resolve three-person mixtures, the other two enhancements did. The final LSD-3 method is capable of resolving, on average, seven or eight of the thirteen loci in STR DNA mixtures under most conditions.