NEW MEXICO STATE POLICE

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Crime Scene Processing Series CRIME SCENE
DIAGRAMMING New Mexico State Police Criminal
Investigations Section Crime Scene Team
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Learning Objectives

• Understand the purpose for preparing a diagram
• Identify the information that must appear on a
  diagram
• Demonstrate knowledge and proficiency in various
  methods of incident scene diagram

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Why do a Crime Scene Diagram?

• It establishes a permanent record of the scene
• Associates evidence with the scene
• Supplements photographs
• Useful in orienting a person to the scene
• Witnesses can look at a diagram without being
  prejudicedyou cant show witnesses photos
• Useful in Court
• Easily blown-up for presentation
• Not prejudicial to the jury

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Why do a Diagram, cont.

• The draw back of photos is that that they are a
  two- dimensional representation of a three
  dimensional object
• Most photos distort the relationship of the
  photographed objects, causing items to appear
  closer or farther apart than they actually are
• The sketch is a bird-eye view, which is hard to
  get with a camera

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Methods

• Grid (X/Y) Coordinates
• Triangulation Coordinates
• Polar Coordinates
• Raw Measurements

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Grid Method

• The scene in divided into four quadrants
• Each item is measured at right-angles from each
  axis
• This is a great method because it is easy
  efficient

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Grid (X/Y) Method
Y axis
X axis
(origin)
The grid can also be expressed as north, south,
east, and west measurements
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Grid (X/Y) Method
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Baseline Method

• Place a single line, dividing the scene in half
• Measure relative to the line
• Alone the baseline
• At a right-angle to the baseline
• Great for a diagram where you have no fixed
  reference points

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Incident Bone Scatter, Death Investigation Locati
on Chavez County, NM Date 3/3/07
Drawn by R. Mathews Not to Scale
REF. PT. 1 N 32 degrees 41.292 W 105 degrees
13.951
skull
Leg bone
torso
North
Leg bone
N
Arm bone
Trees
Arm bone
Dry stream bed
Ref. PT. 2 N 32 degrees 41.317 W 105 degrees
14.003
N
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Triangulation Method

• Straight line distance measured from two (2)
  reference points
• The item of evidence will be at the intersection
  of the intersection of the two (2) arcs
• This is a very accurate method of measuring

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Triangulation Method
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Polar Method

• Straight line distance measured from a fixed
  reference point
• Measure the distance from the reference point to
  the item of evidence
• Document the lines azimuth from the fixed
  reference point to the item of evidence
• This is the best method for determining
  elevations above/below a fixed reference point

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Polar Method
North
12 ft _at_ 120 degrees
18 ft _at_ 100 degrees
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Raw Measurements

• The physical dimensions of a room/area
• You should do this on every diagram to complement
  the main method of measurement
• Width of roads
• Distance from the victims hand to the gun
• Overall dimensions of a room

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Raw Measurements
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Information added to a USGS Map
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Sketching the Crime Scene

• Equipment
• Measuring tapes, rulers
• Hammer, nails, shop clamps
• Laser range-finder
• Graph paper and PENSILS (avoid using a pen)
• GPS
• Maps, blue-prints, aerial photos
• Accident/crime scene templates

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Sketching the Crime Scene

• Its usually prepared in one of two ways
• Birds-eye-view (straight down)
• Elevation (cross section)
• Try to maintain proportionality (scale)
• Double-check your measurements to be sure that
  they are correct
• Especially important if calculations will later
  be used
• Bloodstain pattern analysis
• Accident reconstruction
• Shooting scene reconstruction

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Sketching the Crime Scene

• Crime scene diagram is similar to diagramming an
  auto accident with injuries
• Use fixed reference points and reference lines
• Diagram the location of all evidence, including
  the body
• Diagram the location of the head and the feet if
  practical...otherwise, diagram the location of
  the center-of-mass
• If you start a diagram need to leave, make sure
  you pass on the responsibility to another person

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Rough Draft
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Finished product
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Sketching the Crime Scene

• Use the rough-draft to make a finished (court
  admissible) product
• Hand-drawn is fine if you are a good artist
• Use black ink and good paper
• Use a template
• Computer generated sketches are preferable
• Can be easily reproduced without loss of quality
• Can be easily blown-up or added to Power Point
• Maintain the original, rough sketch
• It is discoverable-just like your other field
  notes

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Things to put in the Legend

• Specific location of the scene
• Address, GPS Coordinate, etc.
• Date/Time
• Case Number
• Preparer
• Scale (or scale disclaimer )
• Compass Orientation (North Arrow)
• Evidence Numbers
• Measurements

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Court room presentations
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Court room presentations
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Court room presentations
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Court room presentations
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Court room presentations
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Questions?