Overview
This lecture explains the major categories of forensic evidence and how to classify different types, focusing on physical, real, known, and class versus individual evidence.
Classification Schemes for Forensic Evidence
- Four major evidence classifications: physical vs. non-physical, real vs. demonstrative, known vs. unknown, and class vs. individual.
Physical vs. Non-Physical Evidence
- Physical evidence refers to tangible items from a crime or accident scene, such as bullets, shoe prints, and blood samples.
- Non-physical evidence includes non-tangible items like eyewitness testimony or expert opinions.
Real vs. Demonstrative Evidence
- Real evidence is generated by criminal activity at the scene, like blood spatter or shell casings.
- Demonstrative evidence is created after the crime to illustrate or explain aspects in court, such as photos, diagrams, and models.
Known vs. Unknown Evidence
- Known evidence has a source identified with certainty at the scene, such as a victim's blood sample.
- Unknown evidence requires laboratory testing to determine its source, for example, unidentified blood spatter needing DNA analysis.
Individual vs. Class Evidence
- Individual evidence can be linked to only one source, such as DNA, fingerprints, or unique wear patterns.
- Class evidence is common to a group and cannot be tied to a single source, like fibers, general blood types, or hair without roots.
Importance of Evidence Classification
- Some evidence fits multiple categories, but distinguishing between individual and class evidence is crucial in forensic investigations.
- The ability to link evidence to a single person can determine the outcome of a trial.
Key Terms & Definitions
- Physical Evidence — Tangible objects from a crime scene.
- Non-Physical Evidence — Non-tangible information like testimony.
- Real Evidence — Evidence created by criminal activity.
- Demonstrative Evidence — Items created to illustrate facts in court.
- Known Evidence — Source identified without lab testing.
- Unknown Evidence — Source identified only after lab testing.
- Individual Evidence — Traceable to a single source.
- Class Evidence — Common to a group, not one source.
Action Items / Next Steps
- Review examples of each evidence category.
- Study the distinction between individual and class evidence for application in case studies.