Crime scene investigation and evidence collection
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Crime Scene Investigation and Evidence Collection. Physical Evidence. Any and all objects that can establish that can establish that a crime has or has not been committed or can link a crime and its victim or perpetrator

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Crime scene investigation and evidence collection

Crime Scene Investigationand Evidence Collection


Physical evidence
Physical Evidence

  • Any and all objects that can establish that can establish that a crime has or has not been committed or can link a crime and its victim or perpetrator

    • In order to be useful it must be collected, preserved and properly analyzed by forensic experts

    • The CSI Myth…Crime laboratories do not solve crimes yet only enhance the ability of investigators to solve crimes by providing them with data.


Types of evidence direct vs circumstantial
Types of EvidenceDirect vs Circumstantial

Direct

Circumstantial

Indirect evidence that can be used to imply a fact yet does not directly prove it

Provides a link between a suspect and a crime Scene.

Can be physical or biological in nature

  • First hand observations such as …

    • Eyewitness Accounts

    • Police Dashboard Cameras

    • Surveillance Cameras

  • Confessions are also considered to be Direct Evidence


Circumstantial evidence physical vs biological
Circumstantial EvidencePhysical vs Biological

Physical

Biological

Body fluids (blood, semen, saliva), hair, natural fibers, plant part (such as pollen) ect...

Usually reduces # of suspects to smaller group or even a single individual

Often more persuasive in court

  • Fingerprints, footprints, shoe prints, tire impressions, tool mark impressions, synthetic fibers, weapons, bullets, shell casings ect…

  • Reduces # of suspects only to a smaller group of people

    • Exception- fingerprints can be individualized and sometimes other physical evidence can be individualized


Types of evidence class vs individual
Types of EvidenceClass vs Individual

Class

Individual

Evidence that narrows the identity of a criminal down to a single individual.

Examples–

DNA (biological)

Fingerprints (physical)

Some other physical evidence

Fragments that fit together like a jigsaw puzzle

Handwriting *

  • Evidence that narrows the identity of a criminal down to a certain group (classification) of people

  • Does not narrow suspects down to a single suspect or criminal.

  • Can exclude some suspects

    • Example- ABO Blood Type, Rh+ / Rh – Blood Type, Shoe size ect…


Types of evidence trace evidence
Types of EvidenceTrace Evidence

  • Small but measurable amounts of physical or biological evidence found at a crime scene

    • Examples… write down a few

      • Fiber from clothing

      • Broken glass fragments

      • Paint chips

      • fingerprints on glass

      • Soil on shoes or tracked into a home

      • Drop of blood on a T shirt

      • Hair on a brush

      • Pollen on clothing

      • Pet hair on clothes or rugs


Locard s exchange principle
Locard’s Exchange Principle

  • Whenever two people contact with each other, a physical transfer occurs

  • exchange of trace materials/evidence may occur between two people or a person and their other environmental surroundings


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