Crime Scene - PowerPoint PPT Presentation

Loading...

PPT – Crime Scene PowerPoint presentation | free to download - id: 6862b5-ZGZiY



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Crime Scene

Description:

Crime Scene - Wikispaces ... Crime Scene ... – PowerPoint PPT presentation

Number of Views:17
Avg rating:3.0/5.0
Slides: 32
Provided by: DougDa7
Category:
Tags: crime | scene | sketch

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Crime Scene


1
Crime Scene
2
  • Essential Question
  • Content Objective
  • Language Objective

3
Crime scene
  • 1st on scene
  • 1st priority people safety
  • 2nd priority secure the scene keep people from
    altering evidence
  • 3rd priority detain suspects/witnesses

4
Questions
  • ASAP as soon as possible
  • Question 1st on scene and witnesses about any
    transient evidence
  • Weather, odors, visibility, pts. Of entry/exit

5
Crime scene process
  • 1 Safety
  • 2 Secure the scene
  • 3 Preliminary survey (boundaries, exits)
  • Narative, photograph, sketch
  • 4 Detailed search
  • Narative, photograph, sketch
  • 5 Record/collect data
  • 6 Final survey release crime scene

6
Preliminary Survey
  • From outside the crime scene do not know
    boundaries of crime scene
  • body may have been dragged
  • drugs may have been dropped while fleeing the
    scene

7
Preliminary Survey
  • Narrative
  • detailed and legible
  • Time line
  • Measure scene and note locations
  • Describe time of day, weather, lighting
  • Written description of physical evidence
  • Names of people involved

8
Preliminary Survey
  • Photograph
  • Before touch or move anything
  • Take photos from different angles
  • Have ruler for scale
  • Photo from outside to inside in order
  • Photograph each piece of evidence individually-
    and from far away

9
Preliminary Survey
  • Sketch key - scale - compass
  • Original sketch is evidence in case
  • Measurement to scale - relative locations
  • Scale gives relationship of sketch to actual
    size
  • Key explains code used in sketch
  • Compass for orientation

10
Detailed survey
  • From within the crime scene
  • Photograph
  • Sketch
  • Narrative
  • Collect evidence
  • Initiate chain of custody

11
  • Chain of custody a list of all persons who came
    into possession of an item of evidence
  •  

12
Custody
  • Samples and data are considered to be in your
    custody when
  • they are in your physical possession
  • they are in your view, after being in your
    physical possession
  • they are in your physical possession and then
    locked up so that tampering cannot occur
  • they are kept in a secured area, with access
    restricted to authorized personnel only.? 

13
Chain of custody
  • Keep the number of people involved in collecting
    and handling samples and data to a minimum.
  • Only allow people associated with the project to
    handle samples and data
  • Always document the transfer of samples and data
    from one person to another on chain-of-custody
    forms
  • Always accompany samples and data with their
    chain-of-custody forms.

14
Control
  • Control physical evidence whose origin is known
    (exemplar), such as blood or hair from a suspect
    that can be compared to crime-scene evidence
  •   Buccal swab swab of inner portion of cheek
    cheek cells are usually collected to determine
    the DNA profile of an individual

15
Collection of evidence
  • Wet items dry them, package them to prevent
    molding
  • Biological items freeze them.
  • Fire arms fixed inside wooden container
  • Fumes (arson) kept in airtight container
  • Collect most delicate items first (transient
    evidence)

16
Physical Evidence
  • Types of physical evidence encountered at crime
    scenes.
  • Difference between the identification and
    comparison of physical evidence.
  • Physical evidence possessing individual and class
    characteristics.
  • Value of class evidence to a criminal
    investigation

17
  • Identification the process of determining a
    substances physical or chemical identity
  • Comparison the process of ascertaining whether
    two or more objects have a common origin
  • Individual characteristics properties of
    evidence that can be attributed to a unique
    source with an extremely high degree of certainty

18
  • Class characteristics properties of evidence
    that can only be associated with a group and
    never with a single source
  •  
  • Reconstruction the method used to support a
    likely sequence of events by the observation and
    evaluation of physical evidence, as well as
    statements made by those involved with the
    incident
  •  

19
The Role of Forensic Science
  • Provide scientific information to the legal
    community
  • Done via reports and testimony
  • A statement of the limitations on conclusions
    drawn from an experimental result is an essential
    element

20
Responsibility of the Analyst
  • May conclude that an evidence object a
    reference object show similar traits
  • Must understand and communicate the limitations
    inherent in the conclusion
  • limitations are a combined function of
  • the nature of the traits
  • the sensitivity and resolution of the detection
    methods
  • the state of the evidence

21
Legal vs. Scientific Questions
  • The law must establish that a crime has been
    committed by defining the corpus delecti (body of
    the crime)
  • All elements that legally define any particular
    crime must be present to proceed
  • The forensic scientist must translate the legal
    question into a scientific question

22
Thinking Forensically
  • A cognitive framework for a forensic investigation

23
Fundamental Principles
  • Transfer
  • Locard Exchange Principle
  • Identification
  • placing objects in a class
  • Individualization
  • narrowing the class to one

24
The Locard Exchange Principle
  • Every time an object comes into contact with
    another object, it either leaves a portion of
    itself or takes a portion of the other object
    with it
  • Every contact leaves its trace

25
Transfer
  • Physical movement of material from one place to
    another
  • 1 mm fiber transferred from a sweater (its
    source) to a sweatshirt (its destination) during
    contact

26
Transfer
  • No physical movement of material
  • a pattern formed when an object makes an
    impression on some receptive substrate
  • shoe stepping in mud (no detectable amount of
    leather left by shoe

27
Identification by Class Characteristics
  • Classes of objects can be progressively narrowed
    by looking at successively more traits
  • Results in continually fewer objects being
    classified as similar to each other
  • If the traits being compared are not unique to
    the source
  • item will possess traits that might be shared
    with a wide variety of sources

28
  • Once an object is identified by class, the object
    can be compared to a reference (known) item
  • determine if it came from that source or some
    other

29
Individualization
  • Individualization answers the forensic
    investigation questions
  • Which one is it? (animate items)
  • Whose is it? (inanimate items)
  • Accomplished by examining traits that are unique
    to a source item
  • any progeny can only have originated from that
    particular source item

30
Individualizing Traits
  • Minutiae of friction ridges on fingers
    (fingerprints)
  • nicks, cuts or gouges in a tire
  • fine striae in the barrel of a firearm
  • DNA markers

31
Individualizing Characteristics
  • If two objects possess individualizing
    characteristics so that the analyst can conclude
    that no other items exhibit this array of traits
  • association is absolute
  • analyst concludes that the items share a common
    origin with each other
  • latent print at crime scene and a reference set
    of prints made at the police station
About PowerShow.com