The Crime Scene Chapter 2. Physical Evidence Any and all objects that can establish that a crime has...
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Transcript of The Crime Scene Chapter 2. Physical Evidence Any and all objects that can establish that a crime has...
Physical Evidence
• Any and all objects that can establish that a crime has been committed or can provide a link between a crime and its victim or a crime and its perpetrator.
• The recognition of physical evidence is essential to the success of the crime lab.
• Types– Direct (testimonial)
• first-hand observations, confessions, video
– Circumstantial• Indirect evidence can imply a fact but not prove it
– Suspects fingerprints at the scene
Class vs. Individual
• Class evidence– Narrows identity to a group of items of people
• Individual evidence– Narrows identity to a single person or thing
• No amount of expensive, sophisticated lab equipment can salvage the investigation if physical evidence is not recognized and correctly collected and preserved.
• In reality only crimes of a serious nature will require evidence collection
What is a crime scene?
• Primary crime scene—site of the original criminal activity – Ex:site of homicide
• Secondary crime scene—site of any subsequent crime. Can be multiple in number– Ex: Where the body was dumped
• All crime scenes are unique and the boundaries of a crime scene are flexible.
ADAPT
– A Assess the crime scene and assist those hurt (Saving lives is most important)
– D Detain the witness (need these guys for questioning)
– A Arrest the perpetrator (many times they will hang around to admire their handy work)
– P Protect the crime scene (this is where the yellow tape comes in)
– T Take notes (notes are very important especially when the case goes to court)
Securing the Crime Scene
• Anyone who enters the crime scene can alter or change the scene and its evidence
• Access should be limited to crime scene personal and a contamination log should be kept.
• Witnesses are separated to prevent collusion.• Must be guarded 24hrs a day until released• A walk-through should be completed
Walkthrough• Preliminary scene survey
• Mentally reconstruct the crime (this can be changed or adapted)
• Determine the boundaries
• Note any temporary evidence that requires immediate processing or protection
• Make a note of weather conditions and take precautions if necessary
Record the Scene
• To preserve the original state of the scene• The original state will only be available for
a limited amount of time• Tools:
– Photography– Sketches– Videography – Notes
Notes
• Must include a detailed written description of the scene with the locations of where physical evidence was recovered
• Must identify the time physical evidence was recovered, by whom, how, and by whom it was packaged and marked
• Tape-recording and narrating a video tape can be faster than writing.
• At some points notes must be transcribed
Videography
• Done without verbal commentary except for factual info such as date and time
• Should include both general and specific areas
• View of the crime scene from the victim’s point of view
Photography
• Done immediately after videotaping
• Better to take too many than to few
• If an object has been moved it can not be returned to be photographed
Search for Evidence
• Depends on the location of the crime
• Evidence searched for depends on the nature of the crime
• Important to note what is missing as well
Uses for Physical Evidence
• Info on modus operandi• Info on corpus delicti • Info used to determine the essential facts of an
investigation• Linking persons, scenes, and objects• Verifying witness statements• ID suspects
– AFIS– CODIS
• ID unknown Substances• Crime Reconstruction
Theories behind searches
• The Linkage Theory– The theory that if investigators can establish
positive links between evidence, the crime scene, and the suspect then the case may be solved
– Ex: Bloody fingerprints on the victim’s wrist and on the door knob would be useful while bloody fingerprints on only the doorknob would be less useful.
Theories behind searches
• Locard’s Theory of Exchange– Transfer evidence is created whenever two
objects come into contact with each other.• Primary transfer---victim bleeding onto floor• Secondary transfer---suspect steps in blood on
the floor and tracks it through the crime scene
Search Methods
• Line– Lots of people walk side by side across some
large area like a field. • Very easy and works well in outdoor areas• Can be modified into the strip method by dividing
the area into a rectangle which is then divided into strips
Search Methods
• Grid– After the line method has been used the area
is searched perpendicular to the original area so that if the searches were over laid they would form a grid
– Benefit is that two different people search the same area
Search Methods
• Wheel– Viewed as a wagon wheel with spokes. Begin
at the center and move outward– Not useful in large areas because the gaps
between searchers become too great.
• Spiral method– Scene is viewed as a circle. Begin in the
center and spiral out or vice versa
Search Methods• Zone method
– Crime scene is divided into zones. Each zone is searched by an investigator then when finished another investigator searches the zone. Works well indoors
• Link Method– Does not follow a geometric pattern. Works
with the linkage theory. Once an item is found investigators then search for the next logical item. Such as if they find a tool mark then they search for the tool that made it.
Evidence from the victim
• The following should be collected:– Victim’s clothing– Fingernail scrapings– Hair samples– Blood– Hand swabs (gunshot residue)– Bullets from the body– Vaginal and oral swabs (if appropriate)
Collect and Package Evidence
• Must be handled and packaged in a way that prevents any change from taking place between when it is removed from the crime scene and delivered to the crime lab.
Evidence
• Each different item or similar items collected at different locations must be placed in separate containers. Packaging evidence separately prevents damage through contact and prevents cross-contamination.
Packaging Evidence
• 1. Choose the right size paper for a bindle.• 2. Place evidence into paper bindle and tape
closed.• 3. Place bindle inside a paper/plastic evidence
bag. Fold bag closed. • 4. Place seal over folded edge.• 5. Collector should write his or her name over
the folder edge.
Bloodstained materials
• Packaging of manila envelopes, paper bags or wrapping papers are used to prevent mold contamination
• Allow to air dry first
Chain of Custody
• A list of all persons who came into possession of an item of evidence
• Should be kept to a minimum
Standard/Reference Samples
• Physical Evidence whose origin is known that can be compared with crime scene evidence
• Substrate controls– Uncontaminated surface material close to an
area where physical evidence has been deposited (particularly used in arson investigation and bloodstain analysis)
Legal Considerations
• Fourth Amendment Right• Warrant-less search
– Emergency circumstances– Prevent immediate loss or destruction of
property– Incident of lawful arrest– Consent of parties involved
• However, when time and circumstances permit a search warrant must be obtained
Mincey V. Arizona
• Four day search conducted without a warrant after the death of an undercover officer during a narcotics raid of Mincey’s apartment.
• Mincey released on appeal due to warrantless search
• “No exigent circumstances to justify a warrantless search”.