DescriptionForensic DNA analysis uses repetitive sequences in the human genome called Short Tandem Repeats (STRs) for human identification. This study has contributed to the building, design, and development of a fast and easy to use software package to calculate the a posteriori probability (APP) on the number of contributors in an STR profile and to calculate the likelihood ratio (LR), a statistic that conveys the strength of a match for a given suspect, as well as the distribution of the LR over random non-contributors. This research specifically deals with the (1) design and implementation of an algorithm for MatchIt (the component that calculates the LR and its distribution); (2) optimization the code to reduce running time; and (3) development of a user-friendly interface.