Validation of a top-down DNA profile analysis for database searching using a fully continuous probabilistic...

Area of Science:

• Forensic Science
• Genetics
• Biotechnology

Background:

• Mixed DNA profiles present interpretation challenges in forensic casework.
• Probabilistic genotyping software is crucial for DNA analysis.
• Previous methods like Slooten's semi-continuous model targeted major contributors.

Purpose of the Study:

• To evaluate the performance of a "top down approach" for interpreting complex DNA mixtures using a fully continuous probabilistic genotyping model.
• To assess the method's ability to discriminate between contributors and non-contributors in constructed and casework profiles.
• To quantify the potential increase in investigative leads from applying this approach to no-suspect cases.

Main Methods:

• Applied a "top down approach" to interpret complex DNA mixtures within probabilistic genotyping software using a fully continuous model.
• Tested the method on constructed DNA mixtures with known contributors and 91 complex profiles from no-suspect casework.
• Compared likelihood ratios (LR) generated by the top down approach to standard interpretation methods.

Main Results:

• The top down approach demonstrated good discrimination power in constructed mixtures.
• Approximately 75% of 91 complex no-suspect casework profiles yielded a link to a database individual.
• The maximum observed LR did not exceed that of standard interpretation, accounting for Monte Carlo variation.

Conclusions:

• The fully continuous top down approach is effective for interpreting complex DNA mixtures, particularly in no-suspect cases.
• This method has the potential to significantly increase investigative leads by linking more profiles to database individuals.
• The approach shows promise for improving efficiency and effectiveness in forensic DNA analysis.