Shedding light on shedders

Area of Science:

• Forensic Science
• Genetics
• Molecular Biology

Background:

• Previous shedder status studies relied on inferred DNA amounts, leading to uncertainties.
• Variability in swabbing efficiency, DNA recovery, and extraction processes affected prior results.
• No prior study quantified DNA deposition, collection, and amplification losses.

Purpose of the Study:

• To accurately measure DNA deposition, collection, and amplification for precise shedder status determination.
• To mitigate uncertainties inherent in previous shedder status assessment methods.
• To establish a reliable method for classifying individuals based on their DNA shedding levels.

Main Methods:

• Donors provided thumbprints on slides at varying times post-handwashing.
• DiamondTM Nucleic Acid Dye and fluorescence microscopy quantified deposited DNA.
• Direct PCR and fluorescence microscopy confirmed complete DNA recovery from swabs and minimized amplification loss.

Main Results:

• All deposited DNA on slides was successfully recovered via swabbing.
• Direct PCR confirmed no DNA loss during the profiling process.
• Individuals were consistently categorized into heavy, intermediate, and light DNA shedders.

Conclusions:

• The developed method accurately quantifies DNA shedding across individuals.
• This study successfully mitigates prior uncertainties in shedder status determination.
• Accurate classification into shedding groups (heavy, intermediate, light) is now achievable.