Discussion ( Criminal Investigation)>>
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Chapter5-CSI.pptxChapter 5 Searching for physical evidence
Crime Scene Investigation
Lisa M. Dadio
Physical evidence
The cornerstone upon which the successful outcome of the case depends
Collect everything that can be construed as evidentiary
Develop a system where relevant physical evidence is recognized and located
Objectives of a crime scene search
The goal is to locate all potentially relevant and meaningful physical evidence, think about linkages
No two cases are alike
The search must be systematic and structured
So, where should you look for evidence?
How should you conduct the search process?
Linkage theory
It explains the interrelations between a crime scene, a victim, a suspect and physical evidence
Understanding the connections between these will help in the search of physical evidence
If associations can be established between 2 or more of these, the case may be resolved
The more the associations, the greater the success in solving the case
Transfer theory
It results when 2 surfaces come in contact with each other
It was established in Locard’s Theory of Exchange
Two types of transfer evidence are trace and pattern
Trace transfer evidence includes fibers, glass, soil and blood
Pattern transfer evidence are imprint and impression evidence
General concepts of crime scene searches
View the crime scene in its entirety
Look for what is not present
In the search for physical evidence, be open minded and objective
Multiple scenes or a large multi faceted scene needs to be triaged and evaluated
Continuity and consistency are crucial
Focal point versus ancillary areas
Use logic, focal points should be attended to first
Focal points are the areas which have the highest probability of containing relevant physical and pattern evidence
Examples are point of entry/exit, path traveled by the suspect, target area of where the crime occurred
Once completely documented, searched and all evidence is collected and preserved than the ancillary area can be searched
What constitutes a crime scene?
Any area or object that may contain relevant physical and/or pattern evidence
Is a body a crime scene?
Is a computer a crime scene?
Is a suspect a crime scene?
Is a motor vehicle a crime scene?
Crime scene search patterns
They are varied and different in style and application
They all share a common goal, what is it?
There is no single correct method for a specific type of crime scene
There are 6 basic search patterns: line, grid, spiral, ray, zone and link
Link method
Is often the most productive and common approach for crime scene searches
It is based on the 4 way linkage theory
The CSI evaluates the scene and then proceeds through the area in a systematic and logical fashion to gather evidence that can be linked
Line/strip method
Great for outdoor scenes because they are large in scope and there are no identifiable zones
It uses the demarcation of the crime scene into a series of lines or strips
Line Method
Grid method
It is a modified double line search
Zone method
Readily identified zones
Wheel/ray method
The crime scene is considered circular
The CSI starts from a critical point and travels outward along many straight lines
Spiral method
Inward spiral, start at the outer boundary and circle the crime scene towards the critical point
Outward spiral, start at the critical point and circle the crime scene towards the outer perimeter
Practical applications
No one crime scene search will work for all crime scene types
An experienced CSI must select the appropriate method
It must be conducted in a methodical, logical and systematic manner
The purpose is to recognize and locate relevant physical evidence
Do not allow search methods to interfere or diminish other critical crime scene functions
