GHEP-ISFG collaborative exercise on mixture profiles (GHEP-MIX06). Reporting conclusions: Results and evaluation.

Area of Science:

• Forensic Genetics
• Molecular Biology
• Genetics

Background:

• The Spanish and Portuguese-Speaking Group of the International Society for Forensic Genetics (GHEP-ISFG) promotes scientific knowledge in forensic genetics.
• The GHEP-ISFG Mixture Commission conducts annual collaborative exercises on autosomal short tandem repeat (STR) mixture profile analysis and interpretation.

Purpose of the Study:

• To assess the analysis and interpretation of autosomal STR mixture profiles in forensic genetics laboratories.
• To evaluate laboratory adherence to international recommendations and reporting standards for DNA mixture analysis.

Main Methods:

• Organized the sixth collaborative exercise (GHEP-MIX06) involving 25 laboratories analyzing complex mock DNA mixture cases.
• Collected and analyzed reports on mixture profile analysis, interpretation, and statistical evaluation (Likelihood Ratio - LR).

Main Results:

• Participating laboratories increasingly validate DNA mixture profile analysis according to international standards.
• Significant variations were observed in the edition and interpretation of mixture profiles among laboratories.
• While most labs used LRmixStudio for statistical evaluation, LR values showed wide variation, potentially due to allelic composition editing and software parameter choices.
• Not all laboratories strictly followed ISO/IEC 17025:2017 recommendations for reporting results.

Conclusions:

• Laboratories need to establish internal validation criteria for editing and interpreting DNA mixtures.
• Continuous training in software handling is essential for improving consistency in forensic genetic analysis.
• Standardization of mixture interpretation and statistical evaluation is necessary to reduce data dispersion and enhance reliability in forensic genetics.