A comprehensive characterization of MPS-STR stutter artefacts.

Area of Science:

• Forensic Science
• Genetics
• Molecular Biology

Background:

• DNA mixture interpretation is complex, especially when minor contributor alleles overlap with major contributor stutters.
• Accurate characterization of stutter sequences is crucial for resolving such ambiguities in forensic DNA analysis.

Purpose of the Study:

• To characterize multiple stutter types using massively parallel sequencing (MPS) data.
• To develop and integrate stutter models into an extended probabilistic genotyping framework.

Main Methods:

• Massively parallel sequencing (MPS) data from 387 single-source samples were analyzed.
• A beta regression model investigated relationships between stutter proportion and explanatory variables like parental uninterrupted stretch (PTUS).
• Fitted stutter models were integrated into an extended probabilistic genotyping model (MPSproto) based on EuroForMix.

Main Results:

• Stutter proportions were significantly explained by the length of the parental uninterrupted stretch (PTUS).
• Different stutter types (n+1, n-1, n+2, n-2, n0) were analyzed separately per locus.
• The extended model incorporating locus-specific stutter types improved probabilistic genotyping results compared to the conventional model.

Conclusions:

• Characterizing multiple stutter types on a per-locus basis enhances the accuracy of DNA mixture interpretation.
• The developed stutter models and integrated probabilistic genotyping approach offer a more robust tool for forensic DNA analysis.