Criminal Investigations Crime Scene Diagrams

1. Criminal InvestigationsCrime Scene Diagrams

2. Learning Goals: • Understand the importance of diagrams. • Know the two methods of measuring objects at a scene. • Perform measurements and complete a diagram of a scene.

3. Crime Scene Diagrams • Done for serious crime scenes and major accidents. • Augments pictures and notes / reports. • Simple, clean, line drawings that indicate the positions of evidentiary objects in relationship to fixed objects at a scene. • Diagrams allow for measurements (unlike pictures).

4. Crime Scene Diagrams • Excellent visual aid which selectively includes significant objects and leaves out unnecessary details. • Will clarify the appearance of the scene and make it easier to comprehend. • Admissible in court and are often used in big blow-up charts.

5. Crime Scene Diagrams • Photographs may not be enough to sufficiently record a scene. • Photographs create a different perspective and do not always depict the exact location of objects or their relationship to each other. • Photographs do not show measurements or true distances. • Photographs may have distortions.

6. Crime Scene Diagrams • Refresh the memory of the investigator. • Refresh memory of the witnesses. • Refresh the memory of the cooperative suspect (who may assist with further details regarding the scene). • Develops a clear understanding of events.

7. Crime Scene Diagrams • More descriptive than hundreds of words. • Can show sequence of events. • Can show trails and patterns of movement.

8. General Rules for Diagramming • Show all objects that have a bearing on the crime scene. • Locations of entrances / exits. • Show which way the door opens / direction of swing. • Location of weapons / evidence relative to the victim and stationary objects. • Windows.

9. Methods of Measuring • Rectangular Coordinate (Baseline Method) • Used indoors. • Use a baseline that is fixed and permanent (wall). • Measure items using a 90 degree angle from the baseline.

10. Methods of Measuring • Triangulation Method (creation of a triangle of known distances) • Primarily used for outdoors. • Used two fixed points of reference. • Measures the object from the two fixed points. (which creates the triangle) • Can have any degree of angle. • May have to establish a secondary fixed point. (drive a spike into the ground)

11. Methods of Diagramming • Overview Projection (most common)

12. Methods of Diagramming • Cross Projection (Used to gain three dimensional perspective

14. Items to be Measured • Measure at least 2 points on an object to be able to properly place that object back into a scene. • A human body will need at least 6 points of reference to be placed back into a scene (head, hands, feet, torso)

15. Items to be Measured • Depends on the object measured. • On a tool or small item, measure to the edges or points. • On a body, measure to the center mass of a particular body part.

16. Three Types of Sketching • Sketch of Locality (gives a picture of the crime scene and it’s environment, i.e. neighboring buildings and roads) • Sketch of Grounds (gives a picture of the scene with it’s surroundings, i.e. a house with it’s property outlined, an office within an entire floor plan)

17. Three Types of Sketching • Sketch of Details (description of crime scene within it’s immediate surroundings, i.e. the room in which the crime was committed)

18. Diagrams Should Include: • Case number. • Address or location descriptor. • Date/Time. • Officer name/serial number. • Type of offense. • Victim’s name. • Entrances/exits/windows.

19. Diagrams Should Include: • Size of scene. • Indicate north with “N” • Show all measurements. • Include a key or legend. • Include a disclaimer of “not to scale” unless working with precision instruments.

20. Diagrams • May be performed by patrol officers on collision investigations, natural death investigations, and/or other cases that need it or where someone requested to have it.

24. Finished Diagram on Graph Paper

25. Diagrams on Graph Paper • Easier to do on graph. • Provides guidelines for line measurements.

26. Diagrams On major crimes and major collision scenes, diagrams will likely be done with computer assisted drawing (C.A.D.) programs.

31. Drawing in 3D • Height • Width • Depth

32. Technological Advances • Computer Aided Drawings (C.A.D.) • Global-Position Satellite Devices (G.P.S.) • Total Station (laser guided measurements)

33. Total Stations

34. Laser Measurements • Similar to a total station.

35. 3D Scene Digitizer • Costly to buy. ($44,900) • Sets up on tripod. • Measures room up to 40 ft.

36. 3D Scene Digitizer • Can create a “wire-frame mesh”. (3D model of a scene)

37. Technological Advances • Reasons why advanced tools are not in use: • Prohibitive costs. • Time to train. • Tech overload. • Prediction: Hand-held or portable devices will measure and diagram scenes quickly and efficiently and lessen a detective’s workload.

38. Artist’s sketch of scene • Shows detail • Eliminates obscurity

39. Things to Remember: • Decide what is to be sketched beforehand. • Don’t sketch until familiar with the scene. • Leave out objects not relevant to the case. • Include only essential information.

40. Things to Remember: • Your diagrams will not be exact, they will be approximate. • Rough sketch to be included with the case file as well as the finished copy.

41. Errors when Diagramming: • Measuring a distance by pacing and then recording results in feet and inches. • Relying on memory alone. • Correctly outlining the dimensions of a room and then placing objects within by mere visual means (no measurements). • Not being able to read your measurements. • Improper measuring device or technique.

42. Practical Exercise • Practice measuring objects within the classroom using the methods given in class.