- 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
Likelihood Ratio Estimates
Likelihood ratio estimates compare the probability of observing a profile if known contributors were the source of the DNA in a mixture (numerator) to the probability of observing the mixed profile if other unknown contributors were the source of the DNA (denominator).
This approach is flexible and can handle differing assumptions as to the possible contributors to a mixed DNA profile. Conclusions are often stated in the following manner: It is 2 million* times more likely that the DNA profile from the mixed stain originated from the victim and suspect rather than two unknown contributors.
* This number used arbitrarily for this example.
