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Incident Scene Field Sketches
While a picture may be worth a thousand words an equally valuable piece of evidence is the incident scene field sketch. It's exactly what the name suggests, a free hand sketch drawn at the incident scene. Its purpose is to portray the physical facts at the scene and to establish the precise location and relationship of objects and evidence. The incident severity will dictate the amount of detail in your sketch; and whether or not it may have to be redrawn into a more finished drawing at a later date. Your sketch creates a mental picture of the scene for those who were not present and will assist with interviewing witnesses, preparing your report and debriefing management or safety committees.
While your investigation is a priority so too is returning the area to production. Sketching the scene allows the investigator to quickly record, and therefore preserve important information about the scene as it was found. Ideally, nothing should be moved at an incident scene before it is photographed and sketched. In fact, drawing the sketch first helps you focus on what photographs you want to take. You can also include in the sketch the position from which photographs were taken which further helps to communicate what took place to viewers.
The field sketch while not drawn to a precise scale should represent items in proportion to other items at the scene. Always fill the size of the paper with the sketch, as it will soon be cluttered with measurements or objects. If there are a large number of items to be measured then list the measurements on a separate sheet of paper. If you want to establish a rough scale, take the longest measurement at the scene and divide it by the longest measurement of the paper being used for sketching or the number of squares on your graph paper. For example, if the longest wall of a room to be shown in the sketch is 80 feet, and you have 40 squares on the long side of your graph paper, each square can represent 2 feet. If the length of your paper is 10 inches, then the scale becomes one-inch equals 8 feet.
The most useful sketch is a basic floor plan that represents the scene from an overhead view. If the height of objects is a factor then a side view sketch may also be required. What's important and what's not? A general rule of thumb is to include anything that might remotely be important. Include easily identifiable points like doors, windows and pillars.
Start with an obvious feature, perhaps the position of the injured worker, and work either clockwise or counterclockwise, or from one end to another so that nothing is overlooked. Show the location of people, equipment, or materials involved in the incident. If there are liquid spills, skid marks, dust or footprints these must be noted as they can change or disappear quickly. Thanks to gravity over 90% of all the evidence you find at an incident scene is on the ground. Don't walk or drive over it as you enter the scene!
Mark the position of North on the drawing. It doesn't always have to be at the top. Sketches are more easily understood by others if the point of entry to the area or room is at the bottom of the page. In a free corner of the sketch be sure to include information as to the date, time, place, the nature of the incident, and the names of the persons measuring and sketching the scene. Include the notation "Not to Scale" because it's simply not possible to have a field sketch that is 100% to scale.
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