Transcript Crime Scene Processing

Crime Scene Processing
Forensics 4
Definition of “Crime Scene”
• Any area where potential evidence is found,
passed through or interacted with
• Primary Crime Scene
– Location of original or first criminal act
• Secondary Crime Scene
– Location of subsequent criminal acts
• Example: The site of a homicide vs. the
location where the body is left
General Processing Procedures
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Secure and protect the scene
Record the scene
Search for evidence
Collect and package evidence
Submit evidence for analysis
Reconstruct scene
1: Secure the Scene
• Often difficult for the first responder in light
of other duties
• Observe immediate scene
– Identify major physical features and safety
concerns
– Persons present
– Paths into and out of area
– Likely boundaries of primary scene
– Restrict access
2: Record the Scene
• Note taking is the most important aspect of
any investigation
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Must be legible
Must be detailed
Must be specific
Must never be discarded
• Many investigators use pocket tape
recorders
2: Record the Scene
• Date, time and weather information of crime and
investigation
• Type of crime
• General location and description of crime scene
• Names of all investigators, witnesses, police
officers, etc.
• Measurements of important features of scene and
surrounding area
• Preliminary sketches, photos and/or video
• Have we entered the secured area yet?
3: Search for Evidence
• General survey first to pick out notable
characteristics
• More photos and sketches
– Photos should be close-ups, mid-range and wide angle
– Use measuring devices where applicable especially on
close-ups
– Rough sketch at crime scene, scaled sketch later
• Search must be systematic and specific
• Generally work from outer edges into center
• Use extreme caution when entering site
3: Search for Evidence
• Search, do not collect evidence
– Leave markers for later retrieval of evidence
– Tape, flags, markers, etc.
• Think 3d, evidence is not always on the
ground
3: Search for Evidence
• Six major search patterns
– Link Method
• Point to point – one item leads to another
• “Bread crumbs”
– Grid Method
• Very complete but time/manpower consuming
– Line/Strip Method
• Often used in very large areas
• Again, personnel intensive
3: Search for Evidence
• Six major search patterns
– Zone Method
• Often used in buildings
• A single room might be a “zone”
– Spiral Method
• Search spirals out in circles from center of incident
– Wheel/Ray Method
• Search fans out in straight lines from center of
incident
• Limited applications
4: Collect and Package
• Use as few people as possible
– Limits collection techniques, contamination and
mistakes
• Collect “most fragile” evidence first
• Method of collection varies with type of
evidence
– This includes the containers evidence is collected in
• Sealed completely and identified
– Keep a separate log of all evidence
• Only once all evidence is collected is the scene
“released” to appropriate personnel
5: Submit for Analysis
• Often not completed by collecting
investigator
• May require specific processes or facilities
5: Submit for Analysis
• Crime Labs
• Can be public or private
• Public labs run by national/state/local law
enforcement agencies
– 4 US Government Labs
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FBI
ATF
DEA
USPS
• Private labs run by person or corporation
– May specialize in one area only (Ex: toxicology)
– Retest evidence already examined by public lab
6: Crime Reconstruction
• Once analysis is complete, reconstructions
often follow
• May involve complex live/computer
simulations
• Investigators try to recreate exactly what
happened
– Very popular in TV’s “CSI”