Biological Evidence
Definition
Any material of biological origin recovered in a forensic context that can yield information relevant to an investigation. Includes blood, semen, saliva, hair, bone, teeth, skin cells, and plant or microbial material.
- Common types
- Blood, semen, saliva, hair, bone, teeth, skin cells
- Also includes
- Plant and microbial material
- Primary use
- Source attribution via DNA profiling
- Degradation risk
- High; heat, moisture, and UV exposure break down DNA
- Field
- Forensic biology
Common questions
How is biological evidence different from other physical trace evidence?+
Biological evidence carries a cellular or molecular origin that allows genetic profiling, so it can individualise a source in a way that fibres or soil generally cannot. That same organic nature also makes it fragile, so packaging, drying, and cold storage protocols matter far more than for inert trace material.
Why is plant or microbial material treated as biological evidence?+
It comes from a living organism and can carry information about location, time since deposition, or contact with a scene, similar to how blood or hair do. Pollen, seeds, or microbial communities can place a person or object at a location even without DNA profiling being possible.
Related terms
- Chain of Custody
- The documented chronological record of who collected, handled, transferred, and examined a piece of evidence. For digital evidence, chain of custody includes...
- Degradation
- The breakdown of DNA by enzymatic, chemical, or physical processes after biological material is deposited. Degradation produces fragmented DNA that may not...
- Mitochondrial DNA (mtDNA)
- DNA located in mitochondria rather than the cell nucleus. Present in hundreds to thousands of copies per cell, making it recoverable from...
- Nuclear DNA
- The approximately 3.2 billion base pairs of DNA contained in the nucleus of most human cells, organised across 23 pairs of chromosomes....
- Touch DNA
- Minute quantities of epithelial cells transferred by skin contact with a surface, without leaving a visible stain. Collected by swabbing contact points...