crimescencinvestigationevidencecollection-091001080950-phpapp01.pdf

3. The goal of a crime scene investigation
is to:
•recognize
•document
• and collect evidence at the scene of a
crime.
Solving the crime will depend on
piecing together the evidence to form a
picture of what happened at the crime
scene.

4. *Physical Evidence-encompasses any
& all objects that can establish that a
crime has been committed or can link a
crime & its victim or its perpetrator.
Evidence can be classified as direct or
circumstantial evidence.

5. *Direct evidenceevidence that (if true)
proves an alleged fact; includes first hand
observations such as eyewitness accounts.
Confessions are also considered direct
evidence. Also police dash videos
*Circumstantial evidence is indirect evidence
that can be used to imply a fact but that does
not directly prove it; but circumstantial
evidence at a crime scene may provide a link
between the crime scene and the suspect.
Circumstantial evidence can be either physical
or biological in nature.

6. Physical evidence includes impressions
such as
• fingerprints
•footprints
•shoe prints
•tire impressions
•tool marks
•fibers
• weapons
•bullets
•and shell casings.

7. Biological evidence includes
• body fluids
• hair
• plant parts
• natural fibers.

8. Evidence can also be divided into class
evidence & individual evidence.
*Class evidence narrows an identity to a group
of persons or things. Ex blood type
*Individual evidence narrows an identity to a
single person or thing.

9. Class Evidence Examples
•Single layered paint
•Soil
•Hairs
•Fibers

10. Evidence that contain Individualizing
Characteristics
•Fingerprints
•Handwriting
•Bullets (striations)
•Toolmarks (striations)
•Shoeprints (wear patterns)
•Tire prints
•Glass fragments that can
be matched

11. Whenever two people come in contact
with each other, a physical transfer occurs.
Hair, skin, clothing fibers, pollen, glass
fragments, any number of different types of
material can be transferred from one person to
another. These transferred materials constitute
what is called trace evidence.
*Trace evidencesmall but measurable
amounts of physical or biological material found
at a crime scene.

12. The first person to note this condition was
Dr. Edmond Locard, director of the world’s 1st
forensic laboratory in Lyons, France.
Locard’s Exchange Principlestates
that when a person comes into contact with an
object or another person, a cross transfer of
physical evidence can occur. The exchanged
materials indicate the two objects were in
contact.
The second part of Locard’s Principle
states that the intensity, duration and nature of the
materials in contact determine the extent of the
transfer.

13. 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 & Collecting evidence

18. The 1st priority at the crime scene is to
preserve life & help any living victims.
The 2nd priority is to detain & question any
suspects & remove them from the scene. Potential
witnesses should be detained, separateddone to
avoid witnesses working together to create a story
(collusion) & questioned.
Police must secure the crime scene to prevent
traffic through the area that may destroy or
contaminate evidence.
In order to be useful, evidence at a crime scene
must be preserved & recorded. Good record keeping
is essential

19. Secure & Isolate the Crime Scene
Destruction or altering of P.E. can occur when a
crime scene is not properly secured & documented.
Investigators only have a limited amount of time to
work a crime site in its untouched state. The
opportunity to record the CS in its untouched state
must not be lost.
Responsibilities of 1st Officer arriving:
1. obtain medical assistance for anyone in need
2. arrest any perpetrators
3. exclude all unauthorized personnel
4. isolate the area

20. Once the C.S. has been secured the lead
investigator will:
1. determine the boundaries of the C.S.
2. establish the perp’s path of entry &
exit
3. proceed w/ an initial walk-through
4. develop a strategy for examining and
documenting the entire C.S.
5. Determination of primary & possible
secondary crime scenes
6. Obvious evidence documented &
photographed.

21. *Primary crime scenethe location
where the crime took place
*Secondary crime scene a location
other than the primary crime scene, but
that is in some way related to the crime,
where evidence is found

22. Record the Scene
the time a C.S. remains untouched is limited;
therefore timely recording of the C.S. is
essential for the investigation and any
subsequent trials
Use of Photography, sketches, & notes are the
3 methods for crime-scene recording.

23. Photography
an unaltered C.S. is most important; objects must NOT be removed
until they have been photographed from all angles.
if any object is moved or removed from the C.S. it should be
noted – under NO circumstance should it be reintroduced
C.S. photos should include not only the immediate scene but
also:
all relevant angles
adjacent areas
close-ups of victim’s relative position in the scene and any
injuries
possible weapons
the area under the body
evidence is photographed as it is found and if size is significant,
a point of reference should be included in the photo
New Technology
digital photos allow near three-dimensional panoramic
views of the crime scene
videotaping the C.S. is rising in popularity – the
investigator must narrate as he/she records the scene

24. "Golden Rule" of Crime Scene
Investigation/Management
"Never touch, change, or alter
anything until it has been
documented, identified,
measured, and photographed . . .
when a body or article has been
moved, it can never be restored
to its original position."

25. Sketches
 Once photos have been taken, the crime-scene investigator sketches
the scene
 * Rough Sketcha draft representation of all essential info &
measurements at a crime scene. This sketch is drawn at the crime
scene. It shows dimensions & location of objects.
 On the sketch, North should be labeled.
 Objects are located in the sketch by distance measurements from 2
fixed points. All measurements are made w/ a tape measure.
 The simplest way to designate an item is to assign it a # or letter. A
legend must be placed below the sketch.
 *Finished Sketcha precise rendering of the crime scene, drawn to
scale.

27. is a constant activity when processing C.S. and
must include:
• detailed written descriptions of C.S. w/
locations of P.E. including also:
• time of discovery
• who found it
• who packaged and marked it
• disposition of item after being collected
•must be detailed enough to refresh one’s
memory months  years after processing
•tape or video recording is advantageous but at
some point it must be transcribed
Notetaking

28. Searching for Evidence
The search pattern selected at a crime scene
depends on the size & locale of the scene & the
# of collectors participating in the search.
Typical examples of crime scene search
patterns are:
1.Grid
2. Linear
3. Quadrant or Zone
4. Spiral

29. Crime Scene Search Patterns
SPIRAL
GRID
LINEAR

30. Securing & Collecting Evidence
1. Evidence can be massive to microscopic
2. may only be detected in a crime lab
ex. traces of blood on clothing, hair and fibers
from vacuum sweeps
3. it is sometimes necessary to confiscate clothing
from victim and perp
4. Critical areas should be vacuumed; sweepings
from different areas must be kept separate
5. finger nail scrapings must also be taken from
suspects and victims

31. Securing & Collecting Evidence
6. Trace evidence should be left on object unless it
is attached to a large object; remove w/ forceps
7. Bloodstains
• scraped if dry
• transferred to moistened swab
• cut out the area of object
8. Each item must be kept separately

32. Securing & Collecting Evidence
All evidence needs to be properly packaged,
sealed and labeled.
The evidence log should contain all pertinent
information including:
•Case #
•Item inventory #
•Description of the evidence
•Name of suspect
•Name of victim
•Date & time of recovery
•Signature of person recovering the evidence
•Signature of any witnesses present

34. Obtaining Standard/Reference Samples
1. Collect evidence from suspects and
victims that are similar to the P.E. collected
@ the scene
paint from vehicles
hair or blood
2. buccal swab
3. substrate control

35. Reference Samples
control samplemust be obtained from victim for
purposes of exclusion
*standard/reference samplephysical evidence whose
origin is known, that can be compared to crime scene
evidence. The presence of reference samples greatly
facilitates the work of the forensic scientist. Ex: blood or hair
from possible suspects to be compared to crime scene
evidence.
* Buccal swabswab of inner portion of cheek,
performed to collect cells for use in determining DNA
profiles
* Substrate controluncontaminated surface material close
to an area where phys evidence has been deposited; used to
ensure that the surface on which a sample has been deposited
does not interfere w/ lab tests

36. Packaging the Evidence
•Evidence is placed in a paper bindle. The size of the bindle depends
depends on the size of the evidence.
•Entire object should be sent to the lab.
• Each different item must be placed in separate containers.
Packaging evidence separately prevents cross contamination.
•Unbreakable plastic pill bottles excellent containers for hair, fiber,
glass evidence
•small amts of trace evidence can be conveniently packaged in a
carefully folded paperdruggist fold: folding one end of the paper
over 1/3, then folding the other end (1/3) over that, & the repeating
the process from the ther 2 sides. After the paper is folded, the
outside 2 edges r tucked into each other to produce a closed
container.

37. Packaging Evidence
• Manila envelopes or sealable plastic bags can be used for
some evidence.
•Wet evidence should NEVER be packaged in plastic
containers while wet.
• Bloodstained materials should NOT be stored in airtight
containers b/c accumulation of moisture may encourage the
growth of mold; in these instances wrapping paper, manila
envelopes or brown paper bags are used.
• All items of clothing must be air dried & place in
individual separate bags.
• Charred debris recovered from a fire must be sealed in
airtight containers to prevent evaporation of volatile
petroleum residue. (new paint cans or tightly sealed jars)

38. Chain of Custody
An evidence log and a chain of custody
document must be attached to every
evidence container.
*Chain of Custodythe documented and
unbroken transfer of evidence; list of all
people who came into possession of an item
of evidence (continuity of possession)
Maintaining chain of custody is essential.

39. Chain of Custody
· every person who handles the evidence must be
accouted for
· all items must be carefully packaged &
marked upon their retrieval at the scene.
· Record to show collector’s initials, location of
evidence, & date of collection.
•Seal the evidence & the collector’s signature is
written across the sealed edge.
• When the package is reopened at the lab it is
opened at a location other than the sealed edge.
Every time opened: new seal, new signature, place
in new evidence bag.

40. Crime Scene Reconstruction
* CRIME SCENE RECONSTRUCTIONinvolves
forming a hypothesis of the sequence of events from before the
crime was committed through its commission;
It’s a method used to support a likely sequence of
events at a crime scene by observing & evaluating physical
evidence & statements made by those involved. Reconstruction
is a team effort that involves putting together many different
pieces of a puzzle.
The collection & documentation of physical evidence
is the foundation of a reconstruction. A reconstruction supports
a likely sequence of events by observing & evaluating physical
evidence & statements made by those involved. The
investigator captures the nature of the scene on an initial walk
through. Using physical evidence he can hypothesize about
what occurred, where it occurred & when it occurred.