Honors Forensic Science

 Crime Labs “run” on physical evidence  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

 To be effective, evidence must be:  Recognized  Collected and processed properly  Collector must be selective using knowledge of crime lab techniques, capabilities and limitations

 Crime labs do not solve crimes  Many jurisdictions have specialized teams to conduct crime-scene searches  Not all crime scenes require retrieval of physical evidence

 First officer(s) on scene should:  Provide medical assistance, if needed, to victims  Arrest perpetrator if present  Preserve and protect area as much as possible

 Exclude all unauthorized personnel from scene  Isolate area using ropes, tape, barricades, guards, etc.

 Lead Investigator should:  Determine boundaries  Determine perp’s path of entry and exit  Document obvious items  Conduct initial walk-through  Develop examination strategy

 Must document the crime scene in original state  Information used in investigation and in court  Monetary limitations may determine method used to document the scene

 Photography  Must be in unaltered condition  Crime scene photographed completely  Items of physical evidence photographed to show position and location; close-ups to show detail  If size is important, include a measurement scale in photo for reference

 Videography  Can be used to augment photography  Can narrate events on videotape  Does not replace photography

 Rough Sketch  Containing an accurate depiction of the dimensions of the scene and showing the location of all objects having a bearing on the case

 Rough sketch should include;  Recovered items of physical evidence  Distance measurements of items (use 2 fixed points)  Legend  Compass heading designating north

 A precise rendering of the crime scene, usually drawn to scale  Often prepared with aid of templates and drafting tools  Reflect same information as rough draft  CAD programs often used

 Must be a constant activity  Should include detailed written description of scene  Detailed description of evidence: location of items, time item discovered, by whom, how and by whom it was packaged, etc.

 Notes often only written record of details  Tape-recording can be advantageous, but still should be transcribed into a written document

 Thorough and systematic, even if seems unnecessary at the time  How crime scene is searched depends on type of crime, local and size of scene, # of collectors, etc.

 Collect massive objects to microscopic traces  Important to collect possible carriers of trace evidence as well as obvious items  Portable vacuum cleaners helpful  Medical examiner may also provide evidence

 Medical examiner may collect and forward:  Victim’s clothing  Fingernail scrapings  Head and pubic hairs  Blood (for DNA typing)  Vaginal, anal, and oral swabs  Recovered bullets from body  Hand swabs from shooting victims

 Prevent change  Change can arise from contamination, breakage, evaporation, accidental scratching or bending, or loss through improper or careless packaging  Maintain evidence in original condition if possible

 Each different item or similar items collected at different locations must be placed in separate containers. Packaging evidence separately prevents damage through contact and prevent contamination

 Chain of custody – list of all persons who came into possession of an item of evidence  Must be established whenever evidence is presented in court  Adhere to standard procedures  Keep to a minimum

 Examination of evidence often requires comparison with known standard or control  Control = physical evidence whose origin is known, such as blood or hair from a suspect, that can be compared to crime scene evidence

 Quality and quantity of controls may help determine evidential value of crime-scene evidence  Controls must be treated with equal care as actual evidence

 Usually submitted personally or by mail shipment  Must be accompanied by evidence submission forms  List of tests to be performed on each item  List of items submitted

 International Association for Identification Safety Committee  Gloves  Particle masks/respirator, goggles, face shield  Be alert to sharp objects  Use biohazard bags  Note taking done with uncontaminated gloves  No eating, drinking, smoking, etc. at crime scenes

 Fourth Amendment – Prohibits unreasonable search and seizure  Mincey v. Arizona  Michigan v. Tyler  When time and circumstances permit, obtain a search warrant before investigating and retrieving physical evidence at crime scene