Chapter 3
Preserving the Crime Scene
Evidence and the Crime Scene

A criminal investigation must be concerned with
both people and things.

Utilizing both human testimony and physical
evidence, a prosecuting attorney can bring a case
against a defendant.
Evidence and the Crime Scene
Evidence:
• Any item that helps to establish the facts of a related
criminal case.
• It may be found at the scene of the crime or on the
victim or taken
from the suspect or
the suspect’s
environment.
Evidence and the Crime Scene
What exactly is forensic science?

Forensic science


The application of science to law, and the use of science and
technology to determine the value of evidence.
Criminalist (or forensic specialist)

A person specifically trained to collect evidence and to make
scientific tests and assessments of various types of physical
evidence.
Evidence and the Crime Scene

In some jurisdictions investigators can call on
these trained technicians to aid in the search
for evidence, and they are often referred to as
crime scene investigators (CSI).
Evidence and the Crime Scene

Eight basic procedures during the crime scene
investigation to gather and preserve evidence:

Recognize or discover relevant physical evidence.

Examine evidence to determine that it can be tested or
compared in a crime laboratory.
Evidence and the Crime Scene

Collect evidence with care and diligence,
according to standard procedures, and in a lawful
manner.

Carefully handle, package, and label evidence to
avoid damage, loss, contamination, or questionable
links in the chain of custody.
Evidence and the Crime Scene

Prioritize Collection of Evidence.

Consider collection based on the evidence. Latent
prints, biological fluids, trace evidence.

Consider environmental conditions into your
process. Rain/wet vs dry/hot
Evidence and the Crime Scene

Carefully record how, where, and by whom evidence
was located to ensure that evidence has not been
tampered with or altered.

Carefully transport evidence to a laboratory,
maintaining the proper chain of custody and security.
Evidence and the Crime Scene

Focus on the easily accessible areas in plain view and
work towards out-of-view areas.

Maintaining your systematic search patterns.

Collect evidence by using a process that does not
compromise other evidence.
Evidence and the Crime Scene

Concentrate on the most transient evidence and work
to the least transient forms of physical evidence.

Remember, the environment can change and affect
evidence.
Evidence and the Crime Scene

Maintain the integrity of the chain of custody
from the crime lab to the court after tests have
been completed.

Present or explain evidence in a court
proceeding, substantiate the find if necessary,
and document the chain of custody.
Evidence and the Crime Scene

The ultimate success or failure of a criminal
investigation depends on:


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Thoroughness exercised at the crime scene
Preserving
Collecting
Recording all available information
Evidence and the Crime Scene
Evidence and the Crime Scene
Pictorial Documentation of the Crime
Scene

Photographs of the scene of a serious criminal
act should be taken as soon as possible after
preliminary investigation priorities have been
taken care of, before
note taking,
sketching, or the
search of additional
evidence begins.
Photographing the Crime Scene



The role of photographs in a criminal
investigation is to present a logical story
visually.
Nothing in the crime scene should be disturbed
before photographs are taken.
When photographing a crime scene, follow the
axiom “More is better.”
Camera Choices
35 mm
 Both black and white and colored film may be used at
the crime scene.

High-speed films are especially useful for capturing
pictures even in low-light conditions.
Camera Choices


Traditionally, a single lens reflex (SLR)
camera has been selected to photograph crime
scenes.
The SLR camera typically is compact and
comes in a variety of formats, from manually
focusing units to fully automatic units
complete with automatic focusing, flash, and
winding.
Camera Choices
Digital
 Digital cameras have a number of advantages
when used in crime scene photography:

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They require no chemical processing
Can be displayed on the camera immediately
Can be transferred to a computer and stored in an
electronic database
Are now accepted in most courts
Camera Choices
Megapixels

Refers to picture image resolution.

A mega equals 1 million.

Pixels are the smallest unit of brightness and color.

More pixels mean sharper, clearer, and better images.
Camera Choices
Video
 Good briefing tool for police officers who
have not visited the crime scene.
 Can be an additional aid for the prosecutor in
presenting a criminal case.
 They are not a substitute, however, for either
photographs or sketches of the crime scene.
Photo Organization

Progress from the general to the specific.
long-range
 mid-range
 close-up


Sometimes it may be necessary to include a
measurement scale in photographs of objects
at a crime scene.
Photo Organization

The first photograph on every roll of film
shot at the crime scene should be a title
card indicating:
Crime location
 Date
 Case identifier
 Photographer
 Roll number

Photo Organization

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River City Police Department
September 4, 2008
1312 Unlucky Drive – Living room
River City CA 92321
RC-08-1622
Officer Widelens
Roll one of three
Sketching the Crime Scene



Sketches are useful in questioning witnesses and
suspects and when writing investigative reports.
Sketches offer accurate information about the
placement of objects.
Sketches show relationships and distances between
things.
Sketching the Crime Scene

For a sketch or diagram to be legally
admissible in court, it must meet the following
requirements:



It must be part of a qualified person’s testimony.
It must recall the situation that the preparer saw.
It must express the place or scene correctly.
Preparing the Sketch

A crime scene
sketch
complements
the notes and
photographs
taken during
the crime scene
investigation.
Preparing the
Sketch
•Try to use the largest scale
possible.
•All sketches should include:
–A compass or an orienting
compass arrow indicating
north.
–A legend or key to explain
letters, numbers, or symbols
used.
–An indication of the scale
used.
Sketching Methods
Rectangular-coordinates method


A sketching method that involves measuring the
distance of an object from two fixed lines at right
angles to each
other.
It is often used to locate
an object in a room.
Sketching Methods
Triangulation method

A sketching method that requires measuring the
distance of an object along a straight line from two
widely separated, fixed reference points.
Sketching Methods

Baseline method

A sketching method that takes measurements along and from
a single reference line, called a baseline, which can be
established by using a length of string, a chalk line, or some
convenient means.
Sketching Methods

Compass point method


A sketching method that requires a protractor or
some method of measuring angles between two
lines.
One point is selected
as the origin and a line
extended.
Sketching Methods

Cross projection method


A sketching method in which the ceiling appears to
open up like the lid of a hinged box, with the four
walls opening outward
Measurements
are then
indicated from
a point on the
floor to the
wall.
Equipment for Sketches

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A supply of pencils (medium or hard lead)
Graph paper and blank paper
A clipboard or other solid portable drawing
surface
A metal tape measure of at least 50 feet
A folding ruler, such as the standard 6-foot
folding ruler used by carpenters, for short
measurements
Equipment for Sketches



A 12- or 15-inch ruler for drawing straight
lines, drawing to scale, or making very short
measurements
A reliable compass or some other means of
finding north
A protractor for drawing and measuring angles
Equipment for Searches

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Latex gloves Compass
Camera, film String
Rope Knife
Evidence tags Steel tape
measure
Assorted containers Ruler
Assorted envelopes Pens
Pill boxes Indelible marker
Magnifier Paper

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Test tubes Fingerprint kit
Plastic bags Shovel
Bottles Flashlight, batteries
Cellophane tape Probing rod
Ax Wire
Saw First-aid kit
Wrecking bar Metal detector
Chalk, chalk line
Discovering and Recognizing
Evidence

After the crime scene has been photographed
and sketched, you can begin a search.
Search Patterns

Spiral search pattern


A search pattern typically used in outdoor areas
and normally launched by a single person.
He or she begins at the
outermost corner and
walks in a decreasing
spiral toward a central
point.
Search Patterns

Strip search pattern


A search pattern in which the space to be searched is
divided into a series of lanes
One or more searchers proceed up and down the
lane, continuing until the area has been completely
searched.
Search Patterns

Grid search pattern


A search pattern that consists of two strip searches,
the second perpendicular to the first
It allows the area
to be viewed
from two angles.
Search Patterns

Zone search pattern

A search pattern in which the area is divided into
four quadrants, each of which is then examined with
one of the other patterns.
Search Patterns

Pie (or wheel) search pattern


A search pattern in which the area is divided into
pie-shaped sections, usually six in number.
Each section is then
searched, usually by a
variation of the strip
search.
Collecting and Marking Evidence

The court will want answers to the following
questions about evidence collected at the crime
scene:

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
Who found it?
What did it look like?
When was it found?
Where was it found, and what is its relation to other
objects at the scene?
Where was it held from its collection to its
presentation in court?
Collecting and Marking Evidence

The investigator who finds the evidence should
place his or her personal identifying mark on it.

The mark should be permanent and capable of
positive identification.

Evidence that cannot be physically marked--such as
bird shot or liquids--should be placed in an
appropriate container.
Collecting and Marking Evidence

This receptacle should then be sealed and
identified with a label or property tag indicating:




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the title of the case
the officer’s name or initials
the date
the time
the specific location where it was found
Collecting and Marking Evidence


A fairly common evidence container in use
today is a 9 by 12-inch manila envelope.
Standard of comparison

A model, measure, or object with which evidence
is compared to determine whether both came from
the same source.
PHOTO LOG
OR
SKETCH