2The Crime Scene processing

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Crime Scene Processing
Crime Scene Processing and
Physical Evidence
Outline
• Define physical evidence
• Crime scene security
• Thorough searching and recording of the crime scene
• Procedures used for conducting a systematic search of a
crime scene for physical evidence
• Proper techniques for packaging common types of
physical evidence
• Concept of chain of custody
• Safety standards at the crime scene
The Crime Scene
• Physical Evidence: any and all objects which can
determine whether crime has been committed or
can provide a link between Crime, Victim, and the
Suspect.
• Locard Exchange Principle: Exchange of
materials between two objects occurs whenever
two objects come in contact with one another.
– A person committing a crime will not only take traces of the
crime scene away with him/her but will also leave traces of
his/her presence behind at the crime scene.
– Therefore the forensic science truly starts at the crime scene.
– The items of physical evidence that are examined by forensic
scientists are retrieved from the crime scene.
Crime Scene Processing and
Physical Evidence
Outline
• Define physical evidence
• Crime scene security
• Thorough searching and recording of the crime scene
• Procedures used for conducting a systematic search of a
crime scene for physical evidence
• Proper techniques for packaging common types of
physical evidence
• Concept of chain of custody
• Safety standards at the crime scene
The Crime Scene
• Crime Scene Security is very
important:
– The way in which the crime scene is
secured, recorded and how all of the
physical evidence is located,
collected, packaged, labeled and
stored are fundamental to the success
of subsequent forensic analysis.
• Preservation of the evidence is
critical
– In this presentation we will explore the
principles, methods and procedures
involved in the processing of a crime
scene to collect all possible physical
evidence related to a crime.
Crime Scene Security
Preservation of a crime scene.
• The first officer(s) arriving on the scene
is responsible to secure crime scene.
• The other first priority of the officer is to
obtaining medical assistance to
individuals that may be injured or those
that need immediate medical help and
arrest the individual that has or may have
perpetrated the crime.
• As soon as it is humanly possible, the
officer should make efforts to exclude all
unauthorized personnel from the scene.
• As the additional officers arrive,
measures are immediately initiated to
isolate the area.
– Ropes or barricades along with the strategic
positioning of guards will prevent
unauthorized access to the area.
• Once the scene has been secured, a
lead investigator will start the process of
evaluating the area.
Crime Scene Processing and
Physical Evidence
Outline
• Define physical evidence
• Crime scene security
• Crime scene examination and thorough searching and
recording of the crime scene
• Procedures used for conducting a systematic search of a
crime scene for physical evidence
• Proper techniques for packaging common types of
physical evidence
• Concept of chain of custody
• Safety standards at the crime scene
Crime Scene Team
•
•
•
•
•
Team leader
Photographer and photographic log recorder
Sketch preparer
Evidence recorder/Custodian
Evidence collection experts
Crime Scene Processing and
Physical Evidence
Crime Scenes cannot be processed without a
warrant
• In the case of Mincey v. Arizona, the
Supreme Court restricted the practice of
conducting a warrentless search at a
homicide scene.
• In the case of Michigan v. Tyler, the Supreme
Court dealt with search and seizure
procedures at a fire scene.
The Crime Scene Examination
• To seek answers to a number of questions.
– Who:
• Who was the victim of the crime?
• Who committed the crime? and
• Who witnessed the crime?
– When:
• When was the crime committed?
– Why:
• Why did the crime happen where it did?
• Why did the crime happen when it did?
The Crime Scene Examination
• Where:
– Where did the key events that produced the
crime scene take place? (For example, in
the case of a body found in suspicious
circumstances, there will be clues present
that indicate whether the person died at the
scene or somewhere else)
– Where and how did the people involved in
the crime enter and, if applicable, leave the
scene?
– Where were those people who were
involved in the crime located at the time of
its initiation, and were they standing,
sitting, kneeling, etc. at that time?
– Where did the objects involved in the
incident originate from and where did they
go to after the crime?
The Crime Scene Examination
• To seek answers to a number of
questions.
– What:
– What was the sequence of events that occurred
during the process of committing a crime?
– What was the motive for committing the
crime?
– What was the modus operandi of the
criminal(s) involved? (Modus operandi: The
way in which the person committing the crime
carries out the act).
– What type of objects (tools, vehicles, weapons,
etc.) was used to commit the crime?
– What was left behind at the scene during the
crime?
– What was removed from the scene during the
crime?
Boston Marathon Bombing
The Crime Scene Examination
• To seek answers to a number of questions.
– Why:
• Why did the crime happen where it did?
• Why did the crime happen when it did?
Crime Scene Processing and
Physical Evidence
Outline
• Define physical evidence
• Crime scene security
• Thorough recording of the crime scene
• Procedures used for conducting a systematic search of a
crime scene for physical evidence
• Proper techniques for packaging common types of
physical evidence
• Concept of chain of custody
• Safety standards at the crime scene
Crime Scene Processing
• To answer questions posed, it is necessary to:
– Preserve the scene in the state in which it was found by restricting access to
trained and authorized personnel only and, where necessary, protecting it from
the elements.
– Record the state in which the crime scene was found via
• note taking,
• photographing,
• video recording, and sketching
– Utilize the data to create a virtual scene(s) using computer graphics for better
understanding of the crime scene and its investigation.
– Construct a systematic log of all actions taken at the scene and by whom these
actions were taken.
– Systematically search and recover of physical evidence.
– Package and label physical evidence.
– Store physical evidence properly.
– Request forensic examination (analysis) of physical evidence.
Crime Scene processing
• All crime scenes are different and the amount of time and effort
required for processing a given crime scene will depend on a
number of factors.
– An assessment of the likely amount of useful evidence that can be collected
from the crime scene, and
– The priorities of the government and the police with regard to the type crime
being investigated.
• For example, serious crimes such as homicide or rape receive
more attention than less serious crimes (volume or petty crime)
such as car theft.
• Further, within the area of volume or petty crimes, not all types of
scene will necessarily be given the same priority.
• Irrespective of the type of crime scene being examined, the
optimum effectiveness of crime scene is achieved only when each
of actions (outlined above) are carried out with due care, diligence
and expertise.
• The investigations should be ethical and follow legal procedures,
e.g., to search the house of suspect, one should have a court order
to do so.
Crime Scene Processing
•
Other factors that are very significant during a
crime scene investigation are as follows:
1. The initial assessment of the scene (type of crime).
2. The management of any risks to the health or safety of both
investigators and the public.
3. The interpretation of the scene in the light of the evidence
gathered.
4. The communication between all individuals involved in the
investigation.
5. Assessment of the intelligence value of the information
obtained from the crime scene.
6. Maintenance of integrity of physical evidence collected from
the scene.
7. Preparation of reports and statements.
8. Presentation of evidence in court, where and when required.
Recording the Scene
• Investigators have only a limited amount of
time to work a crime site in its untouched
state.
• The opportunity to permanently record the
scene in its original state must not be lost.
• Therefore recording the crime scene is critical
• Recording is accomplished via:
– Photography/Videography
– Sketches
– Notes
Sketches (Rough and Finished)
• Sketches:
– Once photographs are taken, the crime-scene investigator should sketch
the scene.
– The investigator may not have skills or time to make a polished sketch
of the scene. However, it is necessary to make a rough sketch
containing an accurate depiction of the dimensions of the scene and
showing the location of all objects
• Finished sketch:
– A sketch drawn with care and concern for aesthetic appearance
– Prepared with the aid of templates and drafting tools by a skilled
individual and is drawn to scale.
– A finished sketch must reflect information contained within the rough
sketch in order to be admissible evidence in a courtroom.
– Computer-aided drafting (CAD) is more commonly used to draw such
sketches.
Crime Scene Sketch
• Fold-down or crossprojection sketch:
– Room is unfolded as if
it is a cardboard box
– Each wall is presented
as a flap extending
from the floor.
Sketches (Rough and Finished)
• Finished sketch:
– A sketch drawn with care and
concern for aesthetic appearance
– Prepared with the aid of
templates and drafting tools by a
skilled individual and is drawn to
scale.
– A finished sketch must reflect
information contained within the
rough sketch in order to be
admissible evidence in a
courtroom.
– Computer-aided drafting (CAD)
is more commonly used to draw
such sketches.
Photography
• Provides an unaltered record of the scene.
• Unless there are injured parties involved, objects must not
be moved until they have been photographed from all
angles.
• Overview photographs: entire scene and surrounding area,
including points of exit and entry, must be included.
• As items of physical evidence are discovered, they are
photographed to show their position and location relative to
the entire scene.
• After the overviews, close-ups should be taken to record the
details of the objects.
• When the size of an item is of significance, a ruler may be
inserted near the object and included in the photograph as a
point of reference.
• Use of videotape at crime scenes is becoming increasingly
popular.
• The same principles used in crime-scene photographs apply
to videotaping.
Notes
• Note taking must be a constant activity throughout
the processing of the crime scene.
• These notes must include a detailed written
description of the scene with the location of items
of physical evidence recovered.
• They must also identify the time an item of
physical evidence was discovered, by whom, how
and by whom it was packaged and marked, and
the disposition of the item after it was collected.
• Tape-recording notes at a scene can be
advantageous-detailed notes can be taped much
faster than they can be written.
• Another method of recording notes is by narrating
a videotape of the crime scene.
Searching the Crime Scene
• The search for
physical evidence
at a crime scene
must be thorough
and systematic.
When looking for an
object that is suspected to
be a specific distance
When most thorough
search is needed
When searching a large
area looking for a large
objects
Large crime scenes
with multiple
evidence collectors
• The search pattern
selected will
normally depend
on the size and
locale of the scene
and the number of
collectors
participating in the
search.
Crime Scene Processing and
Physical Evidence
Outline
• Define physical evidence
• Crime scene security
• Thorough recording of the crime scene
• Procedures used for conducting a systematic search of a
crime scene for physical evidence
• Proper techniques for packaging common types of
physical evidence
• Concept of chain of custody
• Safety standards at the crime scene
Packaging Evidence
• Each different or similar
item of physical evidence
collected at different
locations must be placed
in separate appropriate
containers.
• Packaging each
evidentiary item
separately is important
from the viewpoint of
preventing damage
through contact and
preventing crosscontamination between
items.
Chain of Custody and Collection of controls
• Chain of Custody
– During the collection of evidence, the chain of
custody - a record for denoting the location of the
evidence, must be maintained.
• Collection of controls
– In addition, proper controls, such as hairs, blood,
and fibers, must be collected at the crime scene
and from appropriate subjects for comparison
purposes in the laboratory.
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