How to Draw a Crime Scene Diagram

Written by Aric W. Dutelle

This is an excerpt from the new book by Aric W. Dutelle, An Introduction to Offense Scene Investigation
(Editor'southward Note—The excerpt focuses on documenting a scene with crime-scene sketching and mapping techniques.)

DOCUMENTATION EFFORTS at the crime scene begin the moment that an officeholder gets a call and continue until the case is closed. This is often the most fourth dimension-consuming but besides the most important stride in law-breaking scene investigation. It is the purpose of crime scene documentation to record and preserve the location and human relationship of discovered evidence as well equally the status of the crime scene as it was when the documenter was observing information technology. For the purposes of this text, there are 4 primary methods of documentation that are involved in CSI. These are:

1) Reports and note-taking
(sometimes audio)
2) Photographs
3) Videography
4) Crime scene sketching
and mapping

The cease purpose of documentation should exist the successful annotation of all observations made within the scene of the crime, which volition ensure the individual engaged in the documentation efforts volition best be able to recall the events in the future. Importantly, this information may be presented in court.

Sketching and Mapping the Scene

Sketching—A crime scene sketch is a permanent tape of the size and altitude human relationship of the crime scene and the physical evidence within information technology. The sketch serves to clarify the special information present within the photo-graphs and video documentation, considering the other methods do non allow the viewer to hands gauge distances and dimensions. A sketch is the most simplistic manner in which to present law-breaking scene layout and measurements. Often photographer/camera positions may be noted within a sketch also.

Why is a sketch important to crime scene documentation?

• It accurately portrays the physical facts.
• It relates to the sequence of events at the scene.
• Information technology establishes the precise location and relationship of objects and bear witness at the scene.
• Information technology helps to create a mental picture of the scene for those not present.
• It is a permanent record of the scene.
• It usually is open-door in court.
• Information technology assists in interviewing and interrogating.
• It assists in preparing the written investigative study.
• Information technology assists in presenting the case in courtroom. Well-prepared sketches and drawings assistance judges, juries, witnesses, and others to visualize the criminal offence scene.

When should sketches exist fabricated?

• Sketch all serious crimes and accident scenes later photographs accept been taken and earlier annihilation is moved.
• Sketch the entire scene, the objects, and the bear witness.

Two types of sketches are produced with regards to law-breaking scene documentation: rough sketches, and last/finished sketches. Crude

Figure A—An example of a crude sketch. Courtesy of Sarah Bedish

Figure B—An example of a final sketch. Courtesy of Sarah Bedish

sketches (Figure A) are developed while on-scene, typically during the crime scene assessment/preliminary scene evaluation phase to help with development of a strategic programme for processing. The sketch is not done to scale, can exist drawn with any implement (crayon, chalk, pencil, pen, etc.), and is very rough artistically. As piece of work progresses at the law-breaking scene, the sketch will include non only the crude crime scene layout, but also volition be used to tape measurements of items and structures, and distances between items.

A last sketch (Figure B) is a finished rendition of the crude sketch. They are ordinarily prepared for court presentation and oft will not show all measurements and distances originally recorded on the rough sketch. Only meaning items and structures are typically present inside a final sketch. A final sketch is produced in either ink or on a reckoner, in a manner that is not able to be modified (i.east., not in pencil!). The sketch should exist clutter-free and should accurately depict all pertinent items of evidence, typically through the apply of an accompanying legend. A legend is a notation of explanation, exterior of the sketch surface area, which relates to a specific particular, symbol, or information contained within the graphical representation of a sketch. A final sketch should include:

• Title (What does the sketch represent? For example, Sketch of Depository financial institution ABC Robbery).
• Legend (What practise symbols within the sketch mean?).
• Example Information. (i.due east., date, time, place, case number).
• Initials/Proper name (person who drew the sketch).
• Indication of a direction (east.one thousand., North).
• Calibration (e.g.: one" = 1').
• Measurement table (If measurements are not represented within the confines of the sketch, an accompanying measurement table should be included to explain the distances and measurements associated with information technology.).
• There should be a notation following the scale or measurement table stating: "All Measurements are Approximate." This will ensure that the sketch's author does not get into a credibility argument in court that a measurement is documented as the listed measurement, simply could in fact be greater or lesser due to rounding errors or other factors.

Four unlike offense scene perspectives tin can be represented within a sketch: (a) the bird's eye or overhead view, (b) the elevation or side view, and (c) the 3-dimensional (3D) view. Sometimes personnel cull to comprise several perspectives within a sketch (due east.1000., using both elevation and overhead sketches to draw an exploded or cross-exclusive view of a scene).

An overhead or bird'south eye view is the most common form of crime scene sketching. Information technology is prepared with the perspective being as though the author was looking down upon the scene from above. This type shows the flooring layout but cannot correspond heights of items or bear witness associated prove on walls. In order to show such data, a person must sketch an peak or side view sketch to testify evidence located on a edifice façade, interior wall, or any item of which meridian is an of import aspect (due east.g., death involving a hanging). A 3D crime scene perspective is created with the aid of computers, and has its principal function as being law-breaking scene activity reconstruction, to assist explicate what happened and in what club.

Crime Scene Mapping—Mapping is the term associated with crime scene measurements. Sometimes a person may sketch but not map, meaning that he or she draws a sketch of an area but does non employ measurements to the sketch produced and items represented. Rarely, however, will i map without sketching (i.e., record measurements with no graphical representation for what the measurements represent). Sometimes this footstep is referred to as measuring. There are a variety of methods for mapping a crime scene, depending upon whether the crime scene is an interior or outside scene. As this is an introductory text, only the most basic and most ofttimes used methods are covered hither. The bones types of mapping methods utilized for crime scene sketching and mapping are: (a) baseline, (b) rectangular coordinates, (c) triangulation, and (d) polar/filigree coordinates.

• Baseline Mapping—This is the most bones—and least accurate—form of offense scene mapping. For this method, a baseline is adult or identified from which to conduct measurements. This can be an existing area, such as the edge of a roadway, a wall, contend, etc., or it can exist adult by personnel, such as by placing a string or record measure out through the scene and conducting measurements from there. In the case of the latter, the line should be run between two known stock-still points, such as trees or other identifiable points, so that the points could be found in the future and the scene reconstructed if necessary. Once the baseline is established, measurements are taken from the baseline at an approximate 90 caste angle from the baseline to a point on the identified item or area of the criminal offence scene. Typically, most measurements are fabricated either to centre mass of the detail or to the nearest indicate of the item to the baseline. Because it is impossible to ensure that the measurement was taken at xc degrees, the possibility exists that the measurement will be longer if the measurement was over 90 degrees from the baseline, or if it was less than ninety degrees from the baseline. For this reason, this method is non equally authentic as some of the other methods; however, information technology is quick and extremely like shooting fish in a barrel to utilize.
• Rectangular Coordinate Mapping—The rectangular coordinate mapping method is a slightly more accurate variation of the baseline method because information technology utilizes two such baselines instead of 1. Ii measurements are taken to a point on an item or location at the scene. I from each identified baseline. Some personnel choose to measure to two or more than points on an particular, using multiple rectangular measurements every bit a way of increasing accurateness, while others only cull to measure out to an arbitrarily-identified eye mass of the object in question or point to which the measurements are being taken. As with the baseline method, it cannot be adamant that such measurements are taken precisely at 90 caste angles from the baseline, and then there exists a greater possibility of errors than with some of the other methods. However, due to this method having two measurements, it has much greater accurateness than with the single line baseline method. This method is especially useful in bars spaces and smaller interior scenes.
• Triangulation Mapping—This is the most accurate method that does not make utilize of advanced applied science. While it is quite a fleck more than laborious and time-consuming, information technology is sufficiently more than accurate than the aforementioned methods of mapping to be worth the effort. The accuracy for this method comes in its foundation: two fixed points. From these two fixed points, measurements are taken to specified points on an item or within the offense scene. At that place is no need to worry most whether or not measurements take been made at a right bending considering the points derive from a known fixed point, such every bit the corner of a room, or edge of a door frame. From these fixed points, a minimum of two measurements are made to each identified point. If the object is of a fixed or constant shape (e.chiliad., a firearm or detail of furniture), then the object is measured to two points, from the two fixed points, for a total of four measurements. If the object is of a variable shape or size (e.g., a puddle of h2o, puddle of blood, or pile of wearing apparel), then the object is measured to an gauge eye of mass.
• Polar/Grid Coordinate Mapping—Utilizing polar coordinates is the 4th method of law-breaking scene mapping used to certificate evidence location at a offense scene. Similar those previously mentioned, this is a ii-dimensional organization that indicates the location of an object by providing the bending and distance from the stock-still or known signal. Plain, in social club to conduct measurements by this method a transit or compass is necessary to measure the angles and polar directions. This method is all-time utilized in large outdoor scenes with very few landmarks (e.one thousand., a airplane crash in forest or large field).
• Advanced Mapping Techniques—Some departments may accept the ability to brand meliorate utilization of modernistic technology, such equally global positioning systems (GPS) and Total Stations, which are mapping systems that can take measurements in polar coordinates and and then convert the measurements into filigree coordinates. The benefit of this technology is that they both are able to provide precise electronic distance measurements and are extremely useful in mapping large-scale scenes and events.

A Total Station is an electronic surveying instrument that has an integrated calculator and can measure angles in the horizontal and vertical planes, utilizing a laser rangefinder instead of the more archaic method of a manual tape measure. This is especially useful considering changes in elevation are very difficult to both measure and depict on a crime scene sketch. The Total Station is capable of recording evidence positions in three dimensions, thus simplifying this otherwise complicated situation.

GPS is a satellite-based navigation arrangement comprising a network of 24 satellites that have been placed in the Globe'south orbit by the U.S. Section of Defense. GPS was originally used by and intended for the military; still, in the 1980s the government made the technology bachelor for noncombatant utilize. The benefit of GPS is that information technology works in any weather status, anywhere in the world, 24 hours a day. There are no subscription fees or setup charges to utilize GPS. These satellites complete 2 very precise orbits of the Earth a day, during which they transmit signal information. It is these signals that GPS receivers assemble and so employ triangulation to calculate the user'southward location. A GPS receiver must be locked on to the position signal of at to the lowest degree 3 satellites in lodge to calculate a 2-dimensional position (latitude and longitude) likewise every bit track movements of an object. If the GPS receiver is able to lock onto four or more satellites, the receiver can decide the user's 3-dimensional location (latitude, longitude, and altitude), along with object movement. The more satellites that the GPS is locked onto, the greater the accurateness of the position. Once the user'south position has been determined, an boosted service is that adding of motion can provide GPS users the ability to record information such as speed, begetting, rails, trip distance, distance to destination, sunrise, sunset, time, and many more than possibilities.

How accurate is GPS? In most cases, commercially available GPS receivers are accurate to approximately 12 meters, with higher end units capable of accuracy in the iii- to 5-meter range. This is sufficiently accurate for large scenes that have no known/fixed landmarks. A GPS reading is typically used to "marker" a known point so measurements are made from that location, thereby ensuring that any measurements taken volition all exist "off" past the same amount because they all originate from the same location.

As with all other offense scene measurements, all measurements are estimate, and are never documented as or testified to as being 100% authentic. Crime scene mapping is most doing the best possible documentation with the resource bachelor, realizing that rounding and other factors inhibit the power to be completely authentic.

Nearly the Author

Aric Dutelle is a professor of forensic investigation at the University of Wisconsin-Platteville. His new text, An Introduction to Crime Scene Investigation, was released past Jones and Bartlett Publishers in January 2010. Written to be a single-source reference for the investigative procedure as information technology relates to law-breaking-scene processing methods and procedures, this introductory text takes readers through the day-to-day aspects of criminal offence-scene processing, and describes in detail the crime-scene investigator responsibilities. To learn more most the volume, get to the Jones and Bartlett website: world wide web.jbpub.com

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ORIGINALLY PUBLISHED:
"Documenting the Crime Scene," written past Aric W. Dutelle
An excerpt from his volume, An Introduction to Crime Scene Investigation
January-February 2010 (Volume 8, Number 1)
Evidence Technology Magazine
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Source: https://www.evidencemagazine.com/index.php?option=com_content&task=view&id=184

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