Crime Scene Investigation & Evidence Collection

1. Crime Scene Investigation & Evidence Collection

2. Lessons from the JonBenet Ramsey Case • In 1996, six year-old JonBenet Ramsey was found murdered in the basement of her home. • This crime scene reveals how important it is for crime scene investigators to secure a crime scene immediately or valuable information may be lost forever. • To this day, the case remains unsolved.

3. Goal of Crime Scene Investigation • Recognize, document and collect evidence • The evidence collected at a crime scene is all investigators have to go on to recreate a picture of what happened at the scene.

4. Principle of Exchange • First described by Dr. Edmond Locard (sometimes called Locard’s Exchange Principle) • Defined as the physical transfer of materials such as hair, fibers, blood, and skin cells when two people come in contact with each other • The longer (or more intense) the contact, the greater amount of trace evidence

5. Types of Trace Evidence • Animal or human hair • Fingerprints • Soil or plant material (pollen) • Body fluids (mucus, semen, saliva, blood) • Fiber or debris from clothing • Paint chips, broken glass, chemicals (drugs, explosives)

6. Types of Evidence • Direct evidence – includes firsthand observations, such as eyewitness accounts or police dashboard video cameras and confessions • Circumstantial evidence – indirect evidence that can be used to imply a fact, but does not directly prove it - provides a link between a crime scene and a suspect

7. Circumstantial Evidence • Can be physical or biological • Physical evidence– includes fiber, weapons, bullets, and shell casings • Reduces the number of suspects to a specific smaller group of individuals • Biological evidence – includes body fluids, hair, plant parts, and natural fibers • Makes the group of suspects very small, or reduces it to a likely individual • More persuasive in court

8. Class Evidence vs. Individual Evidence • Class evidence – narrows an identity to a group of persons or things (ex.; blood type) • Individual evidence – narrows an identity to a single person or thing (ex.; fingerprints)

9. Crime Scene Investigative Team • Police officers • District attorney • Crime scene investigators, including recorders, sketch artists, photographers, evidence collectors • Medical examiners • Detectives • Specialists (entymologist, forensic psychologist, toxicologist)

10. Analysis of Evidence • Forensic labs process the evidence and send the results to the lead detective • Unlike CSI, lab techs are specialized and only process one type of evidence • Test results lead to crime scene reconstruction

11. Crime Scene Reconstruction • Involves forming a hypothesis of the sequence of events from before the crime was committed through its commission. • Investigators look at evidence and attempt to determine how it fits into the overall crime scenario.

12. Staged Crime Scenes • Create problems for investigators because the evidence does not match witness testimony • Examples of staged crime scenes • Arson • Suicide/murder • burglary

13. Procedure to Use if Staged Scene is Suspected • Initially treat all deaths as homicides • Do the type of wounds match the weapon used • Could the wounds be self-inflicted? • Establish a profile of the victim through family and friends • Evaluate behavior of victim prior to the event • Evaluate behavior of suspects prior to the event • Corroborate statements with evidential facts • Reconstruct the event • Conduct forensic examinations