by M/Sgt Hayden B. Baldwin, Retired

This page is under construction and is not the final version.

A two day crime scene sketching course has been designed to meet the needs of the law enforcement agencies. This course takes the students from a rough skecth; to final drawings; to computerized drawings; to an overview of 3D video animations. This is a hands on class. The students will be required to complete all phases of the sketching. The instruction method is by slide presentation, video animation tapes, and power point presentation. The students will have hands on and if the course location permits, the students will be able to use several different computer drawing programs.
    It can be very difficult to describe the layout of an area, building or even a single room to someone. However, with the use of a sketch it becomes much easier to describe and understand the floor plan. The prosecuting attorney may use a sketch to demonstrate to the jury the layout of the building. They may ask the witness to indicate on the diagram exactly where he was when he heard the gunshot. This method of demonstrative evidence can far easier explain to the jury what happened and where it happened. The rough sketch that was completed by the crime scene investigator is for the preparation of a finished diagram to be used in a court presentation. The investigator may draw a rough sketch of a scene to aid in their investigation by recording certain important facts that are difficult to put into words.
     The seriousness and type of crime will usually be the determining factor as to whether a crime scene sketch is completed. A simple theft of a bicycle from a rear yard of a residence may not indicate the need for a sketch. However, all homicides and other crimes against persons will require a sketch of the scene.
     A crime scene sketch can demonstrate a true and accurate relationship between objects or the size of the objects. This may be especially true in a fatal hit & run traffic accident. The skid marks on the roadway may appear to be much longer in a photograph than in real life. In a diagram they are accurately depicted and viewed in perspective to the scene. Whether the scene is an outdoor homicide, traffic accident, or an inside crime scene the relationship between objects can be accurately illustrated.
     Crime scene sketches should be considered as crime scene photography is....general, intermediate and close up. In crime scene sketches they are usually considered as an area drawing, single building and a detailed drawing of a room. Outdoors, the sketches would follow the same protocol, general area, intermediate and a detailed close-up.
     It has been well established in court that a well drawn diagram is an aid to the judge, jury and witnesses in visualizing the crime scene. Their admissibility usually lies in their relevance and accuracy. This type of evidence may be referred to as illustrative or demonstrative evidence. Even poorly drawn sketches have been admitted into evidence, as long as they are shown to be fair representations of the scene and it's surroundings.
     Rough sketches made at the scene should be done in pencil so that corrections can be made easily. The scale used is usually determined by the size of paper being used to draw upon. The scale at this point is not important. Always fill the size of the paper with the sketch, it will soon be cluttered with all the measurements or objects. Try to keep the sketch in its proper proportion. If there is a large number of items to be measured than the sketcher should list the measurements on a separate sheet of paper.
     All the equipment that you will need to complete a rough sketch is a piece of paper, pencil, and a measuring device. All finished sketches start with accurate data or measurements. Whether you anticipate a finished two dimensional drawing or an elaborate 3D video animation of the scene, they all start with an accurately measured rough sketch.
    There are three methods of measurement to accurately measure the location of an object. These methods are the rectangular (right angle), triangular, and the base line method. The rectangular method simply uses a right angle (90 degree) from a given flat surface (wall of a structure) to find the distance to the object. Two measurements are required. The triangulation method uses a permanent object, coroners of a room and measure from there to the object, two points are required. The last method, baseline, is usually used in a large outdoor setting. A straight line is marked between two fairly permanent objects (fireplug & a telephone pole) and 90 degree measurements are made of the baseline to the object. In most instances we think of sketches as two dimensional, however we need to remember that space is considered as x, y, & z coordinates. In other words we need to measure the height or depth of objects. This can be illustrated by bullet holes in a wall, or marks on a piece of furniture. For instance, blood spatter interpretation is usually considered as x, y, & z. These same coordinates are measured as previously described.
    For crime scene sketching equipment I would suggest the field investigator use 4 square graph paper (4 squares to an inch), a disposable pencil with an eraser, a straight edge (good 12 inch plastic ruler), a compass for the direction of North, and a 25 foot steel retractable measuring tape. To carry all these objects use an oversize aluminum clip board with a storage compartment. Remember, the persons doing the sketches need to be concerned with bio-hazards at the scene too. They require equipment that can be thrown away if contaminated with bodily fluids or decontaminated with a 10% solution of bleach and water.
     The drawing or sketch is broken down into four parts.....the body, title block, north arrow, and the legend. The body of the drawing is where the sketch is drawn. The title block is normally in the lower right corner and contains the Case number, the date the drawing was completed, the location of the sketch and the name of the sketcher. This is the minimum information required but the title block can include additional information depending on local protocol or needs of the agency. The north arrow normally points up on the paper and the drawing usually is positioned to reflect this ...... I prefer to have the point of entry to the structure or site at the bottom of the paper and let north fall where it may. I do this because it is easier for the witnesses who have entered the structure to orient themselves on the stand when testifying. The last portion of the sketch is the legend. Some agencies have a dual legend, one identifies the objects by alpha designators....i.e., A=Couch, the other legend identifies the evidence, usually by the evidence number. I prefer to use a single legend to identify the location of the evidence.
    All our drawings are marked "Not to Scale" because they are not 100% to scale. Our sketches are measured to within 1/4" of accuracy, whether it is an indoor scene or a large outdoor scene. Some defense attorneys want to argue over the width of a line on the drawing or the inaccurate "metal" measuring tool that can possibly expand or contract depending on the heat or cold. This expansion is minimum and would not be a concern of the investigator.
     Ok, we have addressed the reason for a sketch, the need for accurate measurements and the equipment required. Now how do we complete the finished sketch? The finish sketch is rarely completed at the scene. The finished sketch requires some artistic skills and may beyond the ability of the person completing the rough sketch. The drawing equipment is a fine mechanical pencil, rubber eraser, triangles, compasses, templates for numbers and text, a large drawing board and t-square.......and a lot of patience! The finished drawing is converted to a scale that is reasonable for the display media for court presentation, normally about 3' by 4 '. While this method of completing a finished drawing has been used for years it is now obsolete, or nearly so.
    The advent of the computer changed the way we complete a finished drawing. Now even those who can't draw a straight line can operate a mouse and create a high quality finished drawing in a short time. Several drawing programs have hit the market that allows the investigator to complete a simple two dimensional drawing, all the way  to a complicated three dimensional crime scene illustration...........even to full video animation! The technology is here!

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Crime Scene Sketching Programs

The Cad Zone





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