FORENSIC SCIENCE

FORENSIC SCIENCE

Collection of Physical Evidence • Analysis of Physical Evidence • Provision of Expert Testimony

Collection of Physical Evidence If the investigator cannot recognize physical evidence or cannot properly preserve it for laboratory examination, no amount of sophisticated laboratory instrumentation or technical expertise can salvage the situation. Physical Evidence can achieve its optimum value in criminal investigations only when its collection is performed with a selectivity governed by the collector’s thorough knowledge of the crime lab’s techniques, capabilities, and limitations

2. Analysis of Physical Evidence A forensic scientist must be skilled in applying the principles and techniques of the physical and natural sciences to the analysis of the many types of evidence that may be recovered during a criminal investigations.

Provision of Expert Testimony The forensic scientist must also be aware of the demands and constraints that are imposed by the judicial system. The procedures and techniques that are used in the laboratory must not only rest on a firm scientific foundation but also satisfy the criteria of admissibility that have been established by the courts. Expert witness – an individual whom the court determines possesses knowledge relevant to the trial is not expected of the average layperson

7 Steps: Processing a Crime Scene • Secure and isolate the crime scene • Record the scene: photograph, sketch, take notes • Conduct a systematic search for evidence • Collect and package evidence • Maintain chain of custody • Obtain controls • Submit evidence to laboratory

Secure and Isolate the Crime Scene • 1str responding officer: preserve and protect the area • First priority: obtain medical assistance and arrest perpetrator • Exclude all unauthorized personnel and isolate area; every person that enters the scene has potential to destroy evidence • Determine boundaries and establish the perpetrator’s path of entry and exit; crime scene size will depend of locale of scene, size of area, and victims and suspects

Record the Scene • There is a limited amount of time to permanently record the crime scene in its untouched state • Three methods of recording a crime scene: • Photography • Sketches • Notes

Record the Crime Scene • Photography • Unless there are injured parties, objects must not be moved until they have been photographed from all angles. If objects are moved, photographs may not be admissible in court – unless recorded in notes. • Items to be photographed: • Area in which the crime took place and all adjacent areas • Points of entry and exit from various angles • If indoors, the entire room and wall area as well as adjacent rooms • A body’s position and close up depicting injuries and near by weapons; once the body is removed, the area under the body should be photographed • Physical evidence position and location as well close up (a ruler or other measuring devise may be used as a point of reference) • Videotaping with sound is also a popular method of recording a crime scene

Record the Scene • Notes • Detailed written description of the scene with location of items of physical evidence • Time of discovery of evidence, by whom, how and by whom it was packaged and marked, and the disposition of the item after it was collected • Notes may be the only written record to refresh the memory of the investigators • Tape-recording is commonly done

Conduct a Systematic Search for Evidence • Lead investigator will subdivide the scene into a grid or a spiral

Areas searched must include all probable points of entry and exit • Search for evidence will depend on type of crime: • Homicide -Burglary -Vehicular -Kidnapping • Physical evidence can be a/t from massive objects to microscopic traces • Some objects may only be traceable in laboratory settings therefore the collection of possible carriers of trace evidence is important • Minute traces of blood on clothing • Hair or fibers in vacuum sweepings

The search continues in the autopsy of a deceased victim • Medical examiner determines cause and manner of death • The following should be collected and sent to the forensic lab: • Victim’s clothing • Fingernail scrapings • Head and pubic hair • Blood • Vaginal, anal and oral swabs (in sex related crimes) • Recovered bullets from the body • Hand swabs from shooting victims (gunshot residue) Virtual Autopsy http://www.hbo.com/autopsy/swf/casebook2/casebook2.html

Collect and Package Physical Evidence • Physical evidence must be handled and processed in a way that prevents any change from the crime scene and the time it is received by the crime laboratory • Changes arise through contamination, breakage, evaporation, accidental scratching or bending, or loss through improper or careless packaging • Each different item or similar items collected at different locations must be placed in separate • containers to prevent damage and • cross-contamination.

Examples of packaging containers and techniques: • Plastic pill bottles for hairs, glass, fibers, and other types of small evidence • Manila envelopes or screw-top glass vials for trace evidence (never ordinary envelopes because of possible leaking) • To avoid accumulation of moisture and mold, bloodstained materials should be packaged in manila envelopes or paper bags • Clothing should be air dried and placed in paper bags to allow air flow • Charred debris should be sealed in an airtight container to prevent evaporation

Maintain Chain of Custody • Chain of custody – continuity of possession must be established whenever evidence is presented in court • Standard procedures include • Recording the location of the evidence • Marking it for ID (collector’s initials and date) • Properly completing evidence submission forms for lab analysis • Accounting for every person that handles or examines the evidence.

Standard/Reference Sample • Examination often requires comparison with a known standard or reference sample • Hit and Run might require paint sample from car to compare to paint at scene • Bloodstained evidence must be compared to blood samples or buccal swaps from all people at the crime scene • Evidence may also be compared to substrate controls – materials adjacent to or close to areas where the evidence has been deposited • If a burned area is suspected to be covered in gasoline, it should be compared to a similar area not suspected • Bloodstains on garments should be compared to area without stains

In-Class Crime Scene Assignment: Submit Evidence to the Laboratory • Evidence is submitted by personal delivery or mail shipment depending on the location of the lab • Evidence submission forms should be completed which provides a brief history of the case, the evidence submitted, and the type of analysis that should be preformed • Analyst not strictly bound to specific test requested if new evidence is found or to search for trace evidence • Respond to the crime scene • Collect evidence, record etc. • Turn in a detailed written report of the crime scene investigated

Assignment #1 • Read p. 26-33 • Write a summary of • Crime • Evidence • Forensic Techniques Used • Trial • Findings • Outcomes of the trial for forensic science

FORENSIC SCIENCE