Diagrams and Sketches
Where are you? How do you describe where you are or the location of anything else in the world? Standards have been created throughout history to measure distances so comparisons could be made. Without standards, it would be impossible to efficiently determine exactly what another person meant when describing something.
Where do you start? At the beginning would be the most likely response, but what is that really? For the purpose of this discussion, the beginning is wherever you want to start. At a crime scene, someone must determine the scope of the crime or what perimeter will be appointed to define the scene. Sometimes physical boundaries such as roadways or walls are used, while at other times geographical, or property ownership can be used. Legal requirements such as search warrants and constitutional issues may further define the area. An appropriate measuring device should be chosen depending on the size of the area to be measured. You would not want to use a six inch long plastic ruler to measure the property lines and house location on a 200 acre ranch. In the same way, an aerial mapping system would be useless for determining the size of a doorway to a bedroom.
Each crime scene needs to be described in some detail to allow those who were not there to have a picture of the scene. Photographs are excellent for capturing detail from a single point in space at a time, but they do not show relationships of areas in more than one direction from the photographer at a time. The crime scene diagram is a representation of an area normally viewed as a two dimensional image. Three dimensional sketches can also be completed as well as perspective drawings. In order to produce a drawing, a rough sketch is prepared on scene to identify the basis shape of the area being documented. It should only contain the items of interest as the photographs will contain everything present in full detail. Measurements should be taken of the overall area first. A floor plan is the most common method. It is drawn as if seen from over head which is similar to a bird’s eye view. It will not always be professional looking, but as long as it contains all of the locations and measurements, it will serve the purpose it is intended for. Here is a rough sketch with a number of measurements recorded. A finished sketch is provided to show how the information is converted to a cleaner picture for display.
Bird’s Eye View A drawing depicting what a scene would look like from above or as seen as a bird "flies" over.
Conversion Tables Charts that provide comparative data used to translate one standard to another. Typically weight, length, volume, and temperature
Finished Sketch A drawing produced from a preliminary crude sketch and measurements taken on scene providing a clearer, more accurate depiction of the scene. It may indicate an approximate scale.
Floor Plan A drawing that depicts the basic structure of walls and openings which can be basic or advanced. Measurements and identifiers are normally included in a floor plan.
Perimeter The boundary designated to serve as the outer edge of a crime scene. Access is restricted within the perimeter which may use natural or legal property lines as defining points.
Perspective Drawing A drawing which illustrates how an object would appear from a point in space. One and two point perspective drawings help in line-of-sight investigations. These utilize vanishing points and a horizon line.
Rough Sketch A general drawing of an area with estimated proportions used to document the information required for a finished sketch. Artistically inferior, but detailed in respect to measurements of all items included in the sketch.
Scale Drawing A drawing which can be certified as accurate to a prescribed scale by a licensed engineer or architect. All measurements can be translated precisely from the indicated scale provided.
Standards The official designation of a unit of measure. It is the basis by which all measuring devices are calibrated. Calibration must be completed in order to certify a measuring device as accurate.
Triangulation A geometric means of establishing a fixed position based on the measurements of the three sides of a triangle. Two permanently fixed points are selected and measurements are made to evidence item from each point.