Investigating a Crime - PowerPoint PPT Presentation

1 / 11
About This Presentation

Investigating a Crime


Investigating a Crime CLU3M – PowerPoint PPT presentation

Number of Views:195
Avg rating:3.0/5.0
Slides: 12
Provided by: Andr1384


Transcript and Presenter's Notes

Title: Investigating a Crime

Investigating a Crime
  • CLU3M

Collecting Physical Evidence
  • When a crime has been committed, the first job of
    the police is to collect all the evidence that
    they can find
  • The careful collection, examination, and storage
    of physical evidence are a vital part of any
    criminal investigation.
  • To protect the crime scene, the officers must
    accurately establish two boundaries
  • The centre the area in which the offence was
    actually committed
  • The perimeter the areas surrounding the centre,
    where the offender may have been present or may
    have left evidence

Crime scenes are preserved for 3 reasons
  • To allow for a thorough search of the crime
  • To seize and collect physical evidence.
  • To ensure that the physical evidence is
    admissible in court.
  • Contamination the loss, destruction, or
    alteration of physical evidence

Forensic Science
  • Forensic science is the use of biochemical and
    other techniques to analyze evidence
  • It involves many different disciplines including
    alcohol, anthropology, chemistry, document
    identification and forgery, entomology,
    fingerprints, firearms, trace evidence,
    odontology, biology and pathology

Forensic Science
  • A piece of evidence found at the scene of a crime
    will often be analyzed by several different
    methods to get the most information from it.
  • I.e., a shoe may be examined for bloodstains
    (studied by biology, DNA analysis), trace
    evidence (broken glass or similar type of dirt
    found on suspects shoe and crime scene), gunshot
    residue (may be on suspect's clothes or hands as
    well) etc.

  • Patterns or marks found on surfaces and caused by
    various objects such as figures, shoes, tires,
    blunt objects, etc
  • Impressions have 2 characteristics
  • Class characteristics the general attributes of
    the object i.e. type of tire (Pirelli 15 inch
  • Individual characteristics specific and unique
    of an object i.e. tread wear on a specific tire

  • The unique patterned mark left behind after a
    fingertip touches an object
  • It is unique to an individual and never change
  • There are 2 types of prints
  • Visible fingerprint can be observed by the naked
    eye i.e. coated in blood or grease
  • Latent fingerprint formed by natural oils and
    perspiration on the fingertip. Not visible to the
    naked eye.

Three methods are used to develop latent prints
  1. Graphite powder used on non-absorbent surfaces
    i.e. metal plastic
  2. Iodine fuming used on surfaces such as paper and
  3. Laser beam used to illuminate the print

DNA Testing
  • DNA (Deoxyribonucleic Acid) - is the individual
    blueprint of a human being at a genetic level
  • This is the newest of forensic science methods,
    as it was only developed in the 1980s.
  • It is a very reliable way of linking an accused
    person to a crime..
  • can be found in the form of blood, seminal fluid,
    saliva, or skin.
  • Once a person's DNA has been identified as the
    same as that found at a crime scene, there is a
    tiny chance that that person was not present, as
    only an identical twin would have exactly the
    same DNA.

Forensic Ballistics
  • the science of analyzing firearm usage in crimes.
  • Forensic ballistics involves analysis of bullets
    and bullet impacts to determine the type of
    firearm used.
  • firearm and tool mark examinations also involve
    analyzing firearm, ammunition, and tool mark
    evidence in order to establish whether a certain
    firearm or tool was used in the commission of a

The Crime Scene Continued
  • There are strict procedures on the seizure,
    handling, and storage of evidence
  • no evidence is left unattended
  • the case officer must secure evidence in the
    police property locker
  • transferring evidence is the responsibility of
    the case officer
  • no evidence can be removed from property locker
    without appropriate authority and signature. This
    is to maintain the chain of custody of the
Write a Comment
User Comments (0)