Processing the Crime Scene Securing Physical Evidence http://i.cnn.net/cnn/SPECIALS/2000/columbine.cd/Photos/ENTRYWAY.01.JPG
What is Physical Evidence? Any and all objects that can: establish that a crime has been committed link a crime and a victim link a crime and the perpetrator Selectivity is the key You can’t collect everything!
Priorities at the Crime Scene Obtain medical aid for those in need Arrest the perpetrator Secure the crime scene Exclude unauthorized personnel Remember Locard’s Exchange Principle! Determine crime scene boundaries Locate path of entry and exit
Photography Scene must be unaltered! If objects are removed, positions changed, or items added photos may be inadmissable If items were moved (eg. Securing a firearm) note it in the report, do not put it back! Physical evidence must be photographed to show: Position and location relative to the scene Close-ups to show detail Scale to show size
Sketches Rough sketch records Dimensions of crime scene and surroundings Location of each piece of physical evidence Distances from two points Finished sketch Represents crime scene to the jury
Systematic Search Patterns Spiral search Grid method Strip of line search Quadrant or zone search http://www.tpub.com/maa/12740_files/image598.jpg
Evidence Collection Must collect all possible carriers of evidence Clothing Package each item separately Cross- contamination Sweepings Collect and package each area separately Fingernail scrapings
Evidence Collection Must collect all possible carriers of evidence Head and pubic hairs For comparison purposes Blood or cheek swab for DNA Vaginal, anal and oral swabs For sex crimes Recovered bullets from the body Hand swabs for gunshot residue
Special Considerations for Arson Accelerants Volatile, evaporate easily Collect ash and debris for traces Store in airtight paint cans with vapor concentrators
Standard/Reference Samples To show provenance Substrate Controls you need known Samples of materials reference samples to near where physical compare to evidence was Hair deposited Fiber Want to show tests for physical evidence Glass don’t produce false DNA positives Blood Untouched wallboard in arson Background fabric for blood test
Chain of Custody Key point of attack for the defense Every person who handled or examined the evidence must be accounted for Must be a written record of each hand- off Each time container is opened a fresh seal must be made and initialed
Safety Considerations AIDS and other infectious materials Double gloves, shoe covers, Tyvek suit Blood must be dried Biohazard bags Air-borne particulates and dust Particle mask, respirator, goggles, face shield Sharps and blood contamination No eating, drinking, smoking, putting on make-up
Legal Considerations 4th Amendment Rights Right against unreasonable search and seizure Probable cause Description of place to be searched Description of persons or things to be seized
Searching without a warrant Emergency circumstances Prevent loss or destruction of evidence Search of person and property during an arrest Search made with consent
Key Court Decisions Mincey v. Arizona Undercover cop killed trying to buy drugs Police search scene for four days without obtaining a warrant Supreme Court throws out the evidence found “No exigent circumstances”
Key Court Decisions Michigan v. Tyler Arson at a place of business Police search scene looking for arson but leave scene unattended for several hours Return several times over next 4 weeks to collect evidence without warrant Initial warrantless search is OK after fire Later searches thrown out
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