Y-profile evidence: Close paternal relatives and mixtures

Area of Science:

• Forensic Science
• Population Genetics
• Statistical Genetics

Background:

• Traditional methods for evaluating Y-chromosome profiles face challenges with high mutation rates.
• Calculating match probabilities for Y-chromosome profiles is problematic.
• A novel simulation-based approach was previously proposed to address these limitations.

Purpose of the Study:

• To validate and extend a new simulation-based approach for evaluating weight of evidence (WoE) for Y-chromosome profiles.
• To incorporate familial Y-profile information into WoE calculations.
• To extend the approach to analyze mixtures of Y-profiles.

Main Methods:

• Utilized simulation to describe population distributions of matching Y-profiles.
• Validated robustness against assumptions regarding allelic ladders and founder haplotypes.
• Incorporated Y-profiles of relatives and extended to multi-male Y-profile mixtures.

Main Results:

• The simulation approach is robust to common assumptions in Y-chromosome analysis.
• Incorporating male-line relative Y-profiles modifies the weight of evidence.
• Mixtures of 2, 3, and 4 Y-profiles provide strong evidence, comparable to single-profile matches.

Conclusions:

• The simulation-based method provides a reliable framework for Y-chromosome evidence evaluation.
• Familial information can be effectively integrated into forensic Y-chromosome analysis.
• Y-chromosome mixtures, even from multiple contributors, offer significant forensic weight.