Tool Marks, Questioned Documents, and Biological Evidence
Forensic science utilizes various types of evidence in forensic science to solve crimes, including tool marks, questioned documents, and biological samples. These pieces of evidence provide crucial information that can link suspects to crime scenes and help investigators reconstruct events.
Tool Marks:
As tools are used, tiny nicks and chips form on their edges, creating unique patterns that can be used to identify matches between evidence and suspects. Tools may also pick up traces of blood or other substances that can be tested, or have fingerprints that can be lifted.
Questioned Documents:
Document examiners analyze items such as ransom notes or other suspicious documents to find clues linking them to a crime scene or specific suspect. They examine:
- Type of paper used
- Printing method
- Handwriting style
- Type of ink
- Unique features like watermarks or indentations
Example: Indentations made as someone wrote on a page in a notebook can provide useful clues about the document's origin or content.
Serology and DNA Evidence:
Biological evidence such as blood, semen, saliva, sweat, and urine can provide valuable information about a crime, its victim, or suspects.
Vocabulary: CODIS (Combined DNA Index System) - A database maintained by the FBI used to find matches to unknown DNA samples from crime scenes.
Key points about biological evidence collection and analysis:
- Chemicals and ultraviolet light are used at crime scenes to locate body fluid evidence.
- Potential evidence areas are swabbed, bagged, and collected in airtight vials to prevent cross-contamination.
- DNA can be extracted from various tissues, including hair, fingernails, bones, and teeth.
- DNA profiles created from evidence can be compared to profiles from suspects or victims.
Highlight: The use of DNA evidence and databases like CODIS has revolutionized forensic science, allowing for the identification of suspects and the resolution of cold cases.
