large enough to form a smooth area for drawing.
The investigator should have
available the following items to prepare a rough sketch:
o
Soft lead pencil.
o
50-foot steel tape measure.
o
Straightedge ruler.
o
Magnetic compass.
o
Several thumbtacks to hold one end of the steel tape when the investigator is
working alone.
The finished sketch should be drawn to scale from the information in the rough
sketch. By constructing a scaled drawing, the numbers concerning distances can be
eliminated. The finished sketch need not be prepared by the investigator who drew
the rough one.
But, the investigator must verify the accuracy of the final
product.
It is recommended that a finished sketch be prepared by an experienced
draftsman. The engineer officer of the command may be able to provide a qualified
person for this task. The name of the person who prepared the finished sketch is
indicated in the report and on the sketch.
A copy of the finished sketch is
attached to each copy of the report of investigation.
See Figure 1-6 for an
example.
Methods. There are various methods which can be used to establish the location of
evidence and other important items at the crime scene.
The simplest form of a
sketch is a two dimensional presentation as viewed from directly above.
The triangulation method is used for indoor and inhabited outdoor scenes.
(See
Figure 1-7.) In this method, objects are located and fixed by creating a triangle
of measurements from a single, specific, identifiable point on the object to two
specific fixed points at the scene. Regularly shaped items are fixed by creating
two separate triangles of measurements, each originating at opposite points on the
object and terminating at specific points at the scene. Pliable objects are fixed
by creating a single triangle of measurements from the center-of-mass of the object
to fixed points at the scene plus measuring the longest or widest overall dimension
(pattern size) of the object.
All triangulation measurements must originate and
terminate on the same plane (level).
If movable items are to be used as fixed
reference points, they must first be measured and fixed themselves.
Crime scene
measurements and the triangulation of evidence must be accurate and must be
recorded in the investigative notes and on the appropriate sketches.
MP2004
1-14
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