Cell type determination and association with the DNA donor

Area of Science:

• Forensic Science
• Genetics
• Biotechnology

Background:

• Determining cell material type in forensic stains is crucial for casework.
• Associating specific donors with cell types in DNA samples is challenging, even for single-donor stains.

Purpose of the Study:

• To present a Bayesian network for associating donors and cell types in forensic samples.
• To integrate cell type test performance data (sensitivity, specificity) into DNA profile interpretation.
• To aid in decision-making for further forensic research by performing sensitivity analyses.

Main Methods:

• Developed a Bayesian network model to associate donors with cell types.
• Incorporated literature data on sensitivity and specificity of PSA (seminal fluid), RSID saliva, and RSID semen tests.
• Linked the Bayesian network with software for interpreting mixed DNA profiles.

Main Results:

• The Bayesian network assists in determining the most likely donor-cell type combination.
• Sensitivity analysis reveals the impact of available research data on conclusions.
• Demonstrated that assuming an individual is a donor in mixed profiles can negatively affect donor-cell type associations.

Conclusions:

• The developed Bayesian network provides a framework for interpreting mixed DNA profiles and associating donors with cell types.
• The approach enhances the evidential value of DNA profiles by combining genetic data with cell type information.
• Highlights the importance of considering prior probabilities and test performance in forensic DNA analysis.