A method for interrogating a mixture of nucleic acids in a sample through analysis of short tandem repeat markers to identify the most probable proportion of each nucleic acid in the sample for a defined number of contributors, and the most probable allele sequences for each marker within each nucleic acid from each contributor comprising I. providing a sample which may comprise a mixture of nucleic acids for interrogation; II. amplifying multiple short tandem repeat markers from nucleic acids in the sample to enable amplification of a maximum of two alleles per marker per nucleic acid; III. evaluating data from the amplification such that the number of alleles per marker in the sample, and amounts and relative percentages of each allele per marker in the sample are ascertained; IV. identifying all possible allele pair combinations per marker in the sample from the data; V. predicting the amount and relative percentages of each allele for each possible allele pair combination for each marker in the sample for a defined number of contributors in various proportions; VI. comparing, and calculating the residual (i.e. difference) between the relative percentages of each allele per marker in the sample with that predicted for each possible allele pair combination for each marker for a defined number of contributors in various proportions, and using least square analysis to minimise the sum of squared residuals obtaining the probability for each allele combination for each marker for the defined number of contributors being present in the sample at each proportion, and calculating the mode and median from each residual to check for a consistent mixture proportion ; wherein steps II to VI are repeated numerous times, wherein the numerous times is at least ten, and the probabilities from each repetition for each allele combination for each marker for the defined number of contributors at each proportion are multiplied to identify the most likely allele pair combinations and their most likely proportion in the sample for each marker, and thereby identifying the most likely proportion of nucleic acids in the sample for the defined number of contributors, and the most likely allele sequences for each marker within each nucleic acid from each contributor. I. providing a sample which may comprise a mixture of nucleic acids for interrogation; II. amplifying multiple short tandem repeat markers from nucleic acids in the sample to enable amplification of a maximum of two alleles per marker per nucleic acid; III. evaluating data from the amplification such that the number of alleles per marker in the sample, and amounts and relative percentages of each allele per marker in the sample are ascertained; IV. identifying all possible allele pair combinations per marker in the sample from the data; V. predicting the amount and relative percentages of each allele for each possible allele pair combination for each marker in the sample for a defined number of contributors in various proportions; VI. comparing, and calculating the residual (i.e. difference) between the relative percentages of each allele per marker in the sample with that predicted for each possible allele pair combination for each marker for a defined number of contributors in various proportions, and using least square analysis to minimise the sum of squared residuals obtaining the probability for each allele combination for each marker for the defined number of contributors being present in the sample at each proportion, and calculating the mode and median from each residual to check for a consistent mixture proportion ; <EOS>