- 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 6 :: DNA Lab Report
Topic 3 :: The Significance of DNA Results as Evidence
Interpreting Mixtures
Mixtures of DNA from more than one contributor are commonly encountered. Mixtures of more than one contributor could be due to—
- Actual contribution by multiple donors during the crime.
- Presence of exogenous DNA on the substrate prior to the evidence sample being deposited.
- Contamination during crime scene processing and sample handling (collection, packaging or testing).
Any biological material (blood, semen, saliva, sweat, hair, or other cells left behind after contact) can all be mixed and found in combination with any other.
Click here to view a sample laboratory report containing contact evidence.
Click here to see an animation demonstrating how DNA mixtures at a crime scene can occur.
