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Forensic Science: Fundamentals & Investigations, 2e
Chapter 2
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o chain of custody
o circumstantial evidence
o class evidence
o crime-scene investigation
o crime-scene reconstruction
o datum point
o direct evidence
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Chapter 2
Vocabulary
o first responder
o individual evidence
o paper bindle
o primary crime scene
o secondary crime scene
o trace evidence
o triangulation
Forensic Science: Fundamentals & Investigations, 2e
Chapter 2
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Cengage/NGL/South-Western © 2016
Principle of Exchange
o Locard's Principle of Exchange
• When a person comes in contact with an object or another person, a cross-transfer of physical material can occur.
• The intensity, duration, and nature of the entities and contact determine the extent of the transfer.
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Forensic Science: Fundamentals & Investigations, 2e
Chapter 2
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Cengage/NGL/South-Western © 2016
Types of Evidence
o Direct evidence
• First-hand observations
o Circumstantial evidence
• Indirect evidence that can be used to imply a fact but that does not prove it
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Forensic Science: Fundamentals & Investigations, 2e
Chapter 24
Forensic Science: Fundamentals & Investigations, 2e
Chapter 2
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Types of Evidence (continued)
o Class evidence
• Narrows an identity to a group of persons or things
o Individual evidence
• Narrows an identity to a single person or thing
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Forensic Science: Fundamentals & Investigations, 2e
Chapter 2
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Cengage/NGL/South-Western © 2016
The Crime-Scene Investigation Team
o Police officers
o Crime-scene investigators
o Medical examiners
o Detectives
o Specialists
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Forensic Science: Fundamentals & Investigations, 2e
Chapter 2
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The Seven S’S of Crime-Scene Investigation
1. Securing the Scene
2. Separating the Witnesses
3. Scanning the Scene
4. Seeing the Scene
5. Sketching the Scene
6. Searching for Evidence
7. Securing and Collecting Evidence
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Forensic Science: Fundamentals & Investigations, 2e
Chapter 2All rights Reserved
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Forensic Science: Fundamentals & Investigations, 2e
Chapter 2All rights Reserved
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Packaging Evidence
o The paper bindle is ideal packaging for small, dry, trace evidence.
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Forensic Science: Fundamentals & Investigations, 2e
Chapter 2
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Chain of Custody
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Forensic Science: Fundamentals & Investigations, 2e
Chapter 211
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Forensic Science: Fundamentals & Investigations, 2e
Chapter 2All rights Reserved
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Mapping the Outdoor Crime Scene
o Datum Points and Subdatum Points
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Forensic Science: Fundamentals & Investigations, 2e
Chapter 2All rights Reserved
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Mapping the Outdoor Crime Scene (continued)
o Marking Evidence Collecting Limits
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Forensic Science: Fundamentals & Investigations, 2e
Chapter 214
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Forensic Science: Fundamentals & Investigations, 2e
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Forensic Science: Fundamentals & Investigations, 2e
Chapter 2All rights Reserved
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Mapping the Outdoor Crime Scene (continued)
o Measuring and Marking Evidence Positions
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Forensic Science: Fundamentals & Investigations, 2e
Chapter 2All rights Reserved
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Analyze the Evidence
o Forensic lab technicians are specialized to process only one type of evidence.
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Forensic Science: Fundamentals & Investigations, 2e
Chapter 2
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Crime-Scene Reconstruction
o Crime scene reconstruction involves:
• Forming a hypothesis of the sequence of events from before the crime was committed through its commission
• Comparing the evidence to witnesses statements
o Investigators need to maintain an open mind as they examine all possibilities.
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Forensic Science: Fundamentals & Investigations, 2e
Chapter 2
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Cengage/NGL/South-Western © 2016
Staged Crime Scenes
o Commonly staged types of crime scenes include:
• Arson
• Murder staged to look like a suicide
• Burglary
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Forensic Science: Fundamentals & Investigations, 2e
Chapter 2
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Cengage/NGL/South-Western © 2016
o Locard’s Principle of Exchange states that contacts between people and objects during a crime can result in a transfer of material.
o Evidence may be direct, as in eyewitness accounts, or circumstantial, which does not directly support a fact.
o Evidence may be physical or biological. Trace evidence is a small amount of physical or biological evidence.
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Summary
Forensic Science: Fundamentals & Investigations, 2e
Chapter 2
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o A crime-scene investigation team consists of police officers, detectives, crime-scene investigators, medical examiners, and specialists.
o A crime-scene investigation consists of recognizing, documenting, photographing, and collecting evidence from the crime scene.
o First-responding officers must identify the extent of a crime scene, including primary and secondary scenes when possible, secure the scene(s), and segregate witnesses.
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Summary (continued)
Forensic Science: Fundamentals & Investigations, 2e
Chapter 2
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Cengage/NGL/South-Western © 2016
o After examining the crime scene(s) and identifying evidence, the crime-scene investigators document the scene(s) with photographs and sketches.
o Crime scene(s) are sometimes precisely mapped to ensure that no evidence is overlooked.
o Evidence must be properly handled, collected, and labeled so that the chain of custody is maintained.
o Evidence is analyzed in a forensic laboratory, and the results are provided to detectives, who develop a possible crime-scene scenario.
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Summary (continued)
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