Lecture 1 Flashcards
What factors are considered when determining the boundaries of a crime scene?
Primary focal points, entry/exit points, secondary scenes
Why might the boundaries established by the first responding officer change once the forensic identification officer(s) have arrived?
More experience, scene now controlled and doesn’t need as large space, better lighting to see
What are search patterns?
Organized and methodical means of searching a scene.
What factors are considered when selecting a search pattern? (Seven)
- Location and size of area
- Action of suspects and victims at scene
- Terrain
- Environmental conditions
- Training of searchers
- Physical condition of search teams members
- Number of search team members available
List the five search patterns.
Strip or line search
Grid search
Spiral search
Wheel/ray search
Quadrant/zone search
Define a strip/line search.
One or two investigators start at the boundary at one end of the scene and walk straight across to the other side. They then move a little farther along the border and walk straight back to the other side.
In what type of scene is a strip or line search best suited for?
In a scene where boundaries are well established.
Give examples of scenes where strip or line searches are often employed.
Exterior large scenes, for example, yards, parking lots.
What type of search is depicted in this image?
Strip or line search.
How many people are used in a strip or line search?
1-2
Define a grid search.
Two people performing line searches that originate from adjacent corners and form perpendicular lines.
List a pro and con of grid search.
Thorough, but boundaries must be well established in order to use this method well.
How many people are needed for a grid search?
2
What search pattern is depicted in this image?
Grid search
Describe a spiral search.
Searcher moves in an inward spiral from the boundary to the centre of the scene or in an outward spiral from the centre to the boundary.
How many searchers are used in a spiral search?
1
Which type of spiral search is better: inward or outward? Why?
Inward spiral because you are moving from least destructive to most destructive.
What is a drawback of the spiral search?
Often the complete spiral is not possible and evidence is missed.
What type of scenes are spiral searches common for?
Interior scenes
What search pattern is depicted in this image?
Spiral search
Define a wheel/Ray search.
Employees, several people moving from the boundary straight toward the centre of the scene or from the centre straight to the boundary. I.e. in word or outward.
How many searchers are used in a wheel/ray search?
Several people
Why is the wheel/ray search not preferred?
Because the area is between the rays are not searched.
What search pattern is depicted in this image?
Wheel/Ray search
Define a quadrant or zone search.
Divides the scene into zones or quadrants, and team members are assigned to search each section. Each section can be subdivided into smaller sections for smaller teams to search thoroughly.
What type of scenes are quadrant or zone searches suited for?
Scenes that cover a large area
What should be included in a quadrant or zone search?
All probable points of entry and exit used by the suspect.
What search pattern is depicted in this image?
Quadrant or zone search
What is the objective of plan drawing?
The primary objective is to accurately and objectively record and illustrate the relative spatial locations of both the relevant features of the scene and any evidence within the scene.
Why do we construct plan drawings? (4)
The mapping technician becomes an impartial witness to the spatial aspects of the crime scene, the data will serve us an accurate and reliable basis for a variety of applications, and as a basis for further analysis and expert opinion.
Why do we map when we have other means of documentation?
To ensure the scene and physical evidence are fully and properly documented so as to provide all interested parties with an accurate and objective picture of the scene.
True or false: plan drawings are usually one of the first pieces of evidence introduced at trial
True
List the four groups of people that plan drawings are useful for.
Forensic officer, witnesses, investigating officer, and council, judge and jury.
How do plant drawings help the forensic officer?
Diagrams and models are cross-referenced with photographs, video and
/or notes in order to describe the exact location and relationship of the physical features and evidence within the scene.
How do plan drawings help witnesses?
Helps them to clearly describe their relative positions and the dynamics of the occurrence as it progressed.
How does the plan drawing help the investigating officer?
Serves to place the witnesses in order to help corroborate or refute the accuracy of their statements.
How our plan drawings useful for council, judge and jury?
It assist in understanding the physical layout of the scene: provides distances, and eliminate unnecessary and confusing details.
List some forensic applications that plan diagrams can serve as an investigative tool and presentation device for.
Acoustic analysis, ballistics, blood stain interpretation, burn pattern, mapping, CBRN dispersal, vectors and patterns, vehicle collision, reconstruction, image analysis and rectification, physics, post blast analysis.
When producing a plan drawing, what are the three stages to a successful case preparation?
On scene: preparation, sketching, measuring
Post scene: drawing preparation
In court: testimony
What equipment is need for preparation of plan drawing?
Clipboard, graph paper, 2H pencils, color markers, compass, Post-it notes, data collection system
What methods can be used to sketch a scene?
Tape, scanning or photogrammetry
What are the six basic elements of a formal sketch?
Heading, diagram, legend, title block, scale, direction notations (north arrow)
What should be included in the heading of a sketch?
Notation that indicates why the sketch was created
For example, evidence or measurements, single evidential aspect, such as blood stains or bullet trajectories
What should the drawing itself in a scene sketch do
Should graphically depict the scene and primary evidence
What is the purpose of a legend in a scene drawing?
Indicates what labels used within the diagram depict.
What is the purpose of the title block in a sketch?
Provides important information relevant to the location of the scene and the creator of the sketch
What type of information is typically included in a title block? (four)
Report number, physical address of the scene location, sketch creator, time and date of sketch creation
List the four basic types of sketches
Plan view
Elevation
Exploded view
Isometric
What is a plan view sketch
A floor plan or bird’s-eye view of the scene
What is the simplest and most common type of sketch?
Plan view
What is an elevation sketch?
A side view that portrays a vertical plane rather than a horizontal plane. For forensic purposes, this also includes cross-sections.
What is an exploded view sketch?
A combination of plan view and elevation sketches. Places the plan of a single room in the centre of the drawing and lays each of the four walls flat as if they were hinged along the baseboards.
What is an isometric sketch?
A 3-D drawing combining and depicting three sides without perspective foreshortening.
List the three types of measuring systems.
Direct
Noncontact
Remote
What are the four main factors considered when selecting a measuring system?
Accuracy
Precision
Validity
Confidence
What is meant by accuracy?
How close is the distance as measured to the actual distance?
What is meant by precision?
How consistent/repeatable are the results?
What is meant by validity?
The degree that the system is both accurate and precise
What is meant by confidence?
A measure of overall validity
What additional criteria might be considered when selecting for a measuring system?
Training
Ease of use
Time required
Reliability
Frequency of use
Differentiate between continuous versus additive measuring.
Continuous uses one single reference point while additive uses multiple reference points.
What is a benefit of continuous measuring?
Less susceptible to recording errors
What are benefits of additive measuring?
Can be performed by one person, and requires fewer dimensional lines on the sketch.
List the four methods for crime scene mapping.
Triangulation
Baseline
Right angle offset
Polar
Describe triangulation for regularly shaped objects/evidence.
Four measurements or two triangles made from distinct points or landmarks.
Describe triangulation for irregularly shaped object/evidence.
Two measurements in one triangle made from distinct points or landmarks.
What crime scene mapping method is depicted in this image?
Triangulation
What method of crime scene mapping is depicted in this image?
Baseline
What type of scenes is baseline mapping best suited for?
Exterior scenes without evident landmarks.
And explain the process of baseline mapping.
Start with a data point, a location from which the baseline will extend, which is set by triangulation from fixed landmarks. Measure items of evidence at a right angle from the baseline.
What mapping method is shown in this image?
Right angle offset/rectangular coordinates
How many people does right angle offset require?
1
Right angle offset is a variation of what other type of mapping technique?
Baseline
What is another name for right angle offset measurements?
Cartesian coordinate system
What is likely the most common method of crime scene mapping?
Right angle offset
Describe how right angle offset mapping works.
A location is established based on an X axis and Y axis measurement. For items that have an elevation above or below the ground surface a third measurement along the Z axis will also be obtained.
What mapping method is depicted in this image?
Polar
In what type of scenes is polar mapping best suited for? Give example examples.
Effective for exterior scenes were evidence is scattered over a relatively open area.
Example: aircraft crashes, scattered remains
What type of scenes is polar measuring not suitable for? Give an example.
Not suited for areas where line of site is an issue, for example, forested areas
What materials does polar mapping require?
Surveyors transit, laser sighting device or compass (not best choice)
