CRIME SCENES, EVIDENCE &
FORENSICS
LEARNING DOMAIN 30
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GOAL OF A CRIMINAL INVESTIGATION

An investigation is the systematic gathering of
information from a variety of sources and the
documentation of evidence, observations and findings.

A criminal investigation is a systematic approach to the:
establishment of a criminal violation
 identification and arrest of a suspect, and
 gathering of evidence for presentation in a court of law


REMEMBER: the goal of any criminal investigation is the
successful prosecution of the guilty and exoneration of
the innocent
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PRELIMINARY INVESTIGATIONS

The preliminary investigation begins when the
responding officers first arrive at the scene of the
incident. It continues through the writing and
filing of the primary officer’s investigation report
(w/b p. 3-4)
“the evidence never lies”
Horatio Caine
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COMPONENTS OF THE
PRELIMINARY INVESTIGATION
1)
Arrival: (w/b p. 3-5)

2)
proceed safely to the scene
Assessment:




Determine need for emergency medical services
Verify that a crime has occurred
Identify and arrest suspect(s) if appropriate
Provide dispatch with pertinent info ASAP
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COMPONENTS OF
PRELIMINARY INVESTIGATION
3)
Preliminary Investigation
Secure and protect the crime scene
 Identify and preserve possible evidence
 Locate and interview
victim(s)/witness(es)
 Identify other possible sources of info
4)
Report
Collect available info necessary to write a
clear and effective investigative report
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6
CRIME SCENE PROTECTION
CONSIDERATIONS





Establish an inner and outer perimeter
Assign personnel to maintain
perimeters
Place fixed barriers to maintain
integrity of the scene
Maintain a crime scene log
If necessary, take additional action to
protect the crime scene and physical
evidence
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8
CRIME SCENE SURVEY

Initial survey - Identifies the kinds and
amounts of evidence that may exist at the
crime scene. Purpose gives officers an
opportunity to access, time, equipment,
personnel needed to process the crime
scene.
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10
CRIME SCENE SEARCH

Systematic, coordinated effort conducted in order
to: w/b p. 3-14
1.
2.

Locate physical evidence that a crime has taken place.
Identifies individual (s) who may have committed the
crime.
Search patterns: choice based on type of crime,
size of crime scene, number of personnel
available, personal choice.
a)
b)
c)
d)
e)
Line
Quadrant
Grid
Spiral
Wheel
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ADMISSIBILITY OF PHOTOGRAPHS

Admissible as evidence if
they: (w/b p 3-17)
1. Show an object or person
relevant to the crime
2. Accurately represent,
without distortion, the
object or scene
photographed
3. Are marked properly to
identify contents and
location
4. Are not used solely for the
purpose to appeal to the
emotions or prejudice the
court or jury
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BASIC SURVEY METHODS

Rectangular – Identifies location of an object by it’s
distance from two perpendicular lines.

Triangulation – objects located by determining where
two or more lines intersect (useful out doors).

Coordinate/transect – use when the item of evidence
lies somewhere along a straight line that has
identifiable end points.
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COLLECTION OF EVIDENCE

Prior to collecting, should consider:
 Photographing evidence to demonstrate
appearance when found.
 Diagramming the location and position of items
of evidence to aid in later reconstruction of the
scene.
 Taking notes regarding the physical
appearance of evidence to document condition
in which it was found.
 Wearing appropriate clothing for the type of
crime scene you are working.
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HANDLING EVIDENCE



At risk evidence – that which can be lost,
damaged or contaminated:
 Fingerprints, biological fluids, stains
 Gunshot residue, paint chips, hairs &
fibers, flammable liquids & accelerants
 Shoe, foot, tire impressions
Trace Evidence – very small not seen with
the naked eye
Transfer Evidence – easily transferred
between two objects, i.e. paint chips, hair,
fibers, soil, etc.
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PHOTOGRAPHS

Crime Scene Photos:







Provide visual record of crime scene
Allows court to visualize scene & position of
evidence
Preserves location
of fragile evidence
Can be stored
indefinitely
Show object or person
relevant to the crime
Accurately represent the object or scene
Marked properly to identify contents &
location
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PHOTOGRAPHS

General Guidelines:
 Keep
a detailed log
 Take photos prior to conducting a search
 Take numerous photos from different angles
 Use markers & scale measures in photos
 Use a tripod when available
 Identify photo taker, time & date, location
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EVIDENCE PACKAGING
CONTAINERS





Paper – most dry items
Cardboard – firearms/knives, dried blood
items, that need protection
Metal – chemicals, flammable fluids/items
Glass – items not compatible with metal,
materials with dried biological fluids
Plastic – paper, small amounts of processed
narcotics
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CHAIN OF CUSTODY


The complete and accurate record of
evidence from crime scene to courtroom
Property form formats should include the
following: (w/b p 3-25)
1)
2)
3)
4)
5)
6)
7)
8)
Report number
Who initially found the item
Where and when item found
Item description
Who recovered, packaged, and labeled the item
Who transported
Where submitted
Where, how, and when item was secured
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FORMS OF FINGERPRINTS EVIDENCE

Fingerprints: are a copy or impression of ridges and
valleys present on the outermost layer of human
skin on fingers. Also found on palms, feet and toes.

Visible – impressions in blood, paint, grease, etc

Plastic – impressions left on soft substance such as
heavy grease, melted candle wax, putty, etc

Latent – impressions left by secretions from
perspirations or oils on the skin (normally invisible
to the naked eye until developed)
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