Degradation in forensic trace DNA samples explored by massively parallel sequencing.

Area of Science:

• Forensic Science
• Genomics
• Molecular Biology

Background:

• Short tandem repeat (STR) analysis, a cornerstone of forensic DNA profiling, is often unsuccessful with degraded DNA samples.
• The precise mechanisms and patterns of DNA degradation within biological stains remain largely uncharacterized.
• Understanding DNA degradation is crucial for improving forensic analysis of aged or compromised samples.

Purpose of the Study:

• To investigate the genomic distribution of DNA degradation in aged biological stains.
• To determine if specific genomic regions exhibit differential resistance to degradation.
• To assess the potential for identifying inherently stable DNA regions for enhanced forensic analysis.

Main Methods:

• Massively parallel sequencing (MPS) was employed to analyze DNA from old semen and blood stains.
• Sequence data coverage across the genome was utilized as a quantitative measure of DNA degradation.
• Comparative analysis of degradation patterns was performed across different genomic locations.

Main Results:

• The study revealed that DNA degradation occurs uniformly throughout the genome.
• No evidence was found for specific regions of the genome being more or less susceptible to degradation.
• Sequence data coverage consistently reflected degradation levels irrespective of genomic location.

Conclusions:

• DNA degradation in forensic samples is a non-selective process across the genome.
• The absence of degradation-resistant regions precludes their use for optimizing degraded DNA analysis.
• Current forensic STR analysis limitations with degraded DNA cannot be overcome by targeting specific genomic regions.