Method and system for DNA mixture analysis

A method of analyzing a DNA mixture comprised of the steps:

• (a) obtaining a DNA mixture that contains genetic material from at least two contributing individuals;
• (b) amplifying the DNA mixture in a DNA amplification process to produce an amplification product comprising DNA fragments;
• (c) producing from the amplification product a signal comprising signal peaks from the DNA fragments;
• (d) detecting signal peak amounts in the signal, and quantifying the amounts to produce DNA lengths and concentrations from the mixture to form quantitative genotyping data;
• (e) assuming a genotype value of alleles for a contributor to the quantitative genotyping data at a genetic locus;
• (f) setting a mixture weight value for a relative proportion of the contributors to the quantitative genotyping data;
• (g) forming a linear combination of the genotype values based on the mixture weight value;
• (h) deriving with a computer a data variance of the amplification process from a model that includes both the quantitative genotyping data and the linear combination;
• (i) determining with the computer a probability of the quantitative genotyping data corresponding to a set of suspects from the DNA mixture at the locus using both the linear combination and the data variance value;
• (j) computing a probability of a genotype for one of the contributing individuals using the determined probability of the quantitative genotyping data;
• and (k) comparing the genotype probability with a set of suspect genotypes to identify a likely suspect.