Identification of Mixtures of Two Types of Body Fluids Using the Multiplex Methylation System and Random Forest...

Area of Science:

• Forensic science
• Molecular biology
• Genetics

Background:

• Body fluid mixtures are common in crime scenes.
• DNA methylation assays can identify human body fluids.
• Existing methods show excellent performance for single-source fluids.

Purpose of the Study:

• Develop a methylation SNaPshot multiplex system for body fluid identification.
• Accurately predict body fluid mixtures and their proportions.
• Explore the value of DNA methylation in forensic mixture analysis.

Main Methods:

• Tested 420 body fluid mixture samples and 250 single body fluid samples.
• Utilized an optimized multiplex methylation system with 10 markers.
• Developed two random forest classification models for prediction.

Main Results:

• Observed significant differences in methylation levels between mixtures and single fluids.
• Achieved high prediction accuracy for mixture types (up to 100%) and proportions (up to 98.8%).
• Demonstrated strong correlation between methylation levels and component proportions in mixtures.

Conclusions:

• The multiplex methylation system shows excellent capability for identifying forensic body fluid mixtures.
• DNA methylation analysis is a powerful tool for forensic mixture identification.
• The developed system accurately predicts mixture composition and proportions.