- 01 Introduction
- 02 Biology of DNA
- 03 Practical Issues Specific to DNA Evidence
- 04 Introduction to the Forensic DNA Laboratory
- 05 Assuring Quality in DNA Testing
- 06 Understanding a Forensic DNA Lab Report
- 07 Statistics and Population Genetics
- 08 Mitochondrial DNA & Y-STR Analysis
- 09 Forensic DNA Databases
- 10 Collection of DNA Evidence from Suspects and Arrestees
- 11 Pretrial DNA Evidence Issues
- 12 Victim Issues
- 13 Trial Presentation
- 14 Postconviction DNA Cases
- 15 Emerging Trends
Principles of Forensic DNA
for Officers of the Court
for Officers of the Court
Module 7 :: Statistics
Topic 4 :: Interpreting Mixtures
Calculation of Random Match Probability for Mixed Samples
Random match probability can be calculated in mixtures that involve two contributors and one contributor is known. For example, in sexual assault cases a vaginal swab is analyzed for the presence of semen and a DNA profile is developed from the sperm fraction and non-sperm fractions.
In some cases, as mentioned above, the sperm fraction results in a mixed sample that is consistent with the victim and the sperm donor. If the mixture reveals four alleles—14, 15, 16, and 17—and the victim is known to contribute the 14 and 15 alleles, it can be inferred that the sperm donor must be responsible for the 16 and 17 alleles.
