Basic Crime Scene Sketching

Chapter 2

•Thanks to Special Agent Thompson for helping Mrs. Warren put this together

Sketches

• Hand-made pictorial representation of conditions at a crime scene

• Helps to clarify investigative data

• Explains the relative position, appearance, and condition of physical things which may be material to the investigation

Purpose of sketch is for reconstruction of crime scene

When do we sketch?

• Death scenes

• Serious personal injury

• Sex crimes

• Serious property damage

• Whenever necessary to convey the facts

• FBI always sketches

Sketches Supplement Photos

Photographs• Provide great detail• Do not always show

true and accurate relationships

• Cannot determine distances

Sketches• Eliminate

unnecessary detail• Show true and

accurate relationships• Determine distances

Secure the Scene• Exclude everyone without an official function

• Approach scene carefully and systematically Have a plan!

• Preserve the relationships of objects– Do not alter the position of any object until

photographed and recorded– Position, location, or relationship to other items is

often as important as the object itself– Record through notes, photographs, and

sketches

Materials Required

• Clipboard

• Pencil and ERASER

• Ruler

• Tape measures

• Compass

Reference Points

• Must be accurately described on sketch• Must be relatively permanent (likely to still be

there 10 years later• Fixed points

– Door frames– Room corners

• Outside– Utility poles– Manhole covers– Building corners

• Can be created (iron stake)

Three sketch methods1. Baseline

– Used 90% of the time– Establish a baseline (points A and B) and

describe all evidence in relation to these points• Typically use the back of the room, but can use

other places (like the middle of the room)

– Show outline of the room, doorways, and all evidence• Leave out things that are not relevant

– All measurements go on table, no measurements on sketch

Baseline example

Item Baseline Distance from baseline

1 = Casing #1 3 ft. 12 ft. 4”

2 = Gun 5 ft. 8” 7’ 2”

3 = Casing #2 6’ 4” 7’ 2”

4 = Body 17’ 4” 10’ 6”

A B

A = NW cornerB = NE cornerA → B = 24 ft.

N

S

EW

Three sketch methods

2. Triangulation• Quickest method when only have a few

items• Need two reference points• Measure distance to item from each

reference point• Again, put data in a table, not on sketch

itself

Triangulation Example

A B

N

S

EW

A = Base of door frame, west

B = Base of door frame,east

Item A B

#1 12’ 2” 10’ 6”

Three sketch methods

3. Rose Compass• Used by FBI ERT

members• Best for outdoors• Orient with a magnet

compass so that 0° is aligned with north

• Only reference point is the center

• Triangulate to center• Can use iron stake

Item Degrees Distance

1 45 ° 32’ 6”

2 330 ° 28’ 7”

3 85 ° 42’ 1”

Important Considerations

• Write down all measurements• Fill in all details on rough sketch while at

the scene• Do not sketch on the same paper as the

notes• Measurements must be accurate (within

reason)• Critical distances should be checked by

two officers

Required Information

• On ALL sketches include in a title block:– “NOT TO SCALE”– Magnetic north– Case number– Date– Location (address)– Name of sketcher and any assistants

Clean Sketch

• Clean sketch is done with a ruler back in the office– Typically still not drawn to scale– Usually don’t use graph paper

• Retain rough sketch as notes