Chapter 2 Johnston High School Forensics The Crime Scene Chapter 2 Johnston High School Forensics

Learning Goals Define physical evidence Discuss responsibilities of first officer arriving at scene Explain steps to be taken to thoroughly record crime scene Describe proper procedures for conducting systematic search for evidence

More learning goals… 5) Describe proper techniques for packaging common types of physical evidence 6) Define and understand concept of chain of custody 7) Understand contributions of the forensic pathologist, entomologist, and anthropologist can make to a homicide investigation

Physical Evidence Physical Evidence: Any object that can establish that a crime has been committed or can link a crime to its victim or its perpetrator.

Importance of Evidence Forensic Science begins at the crime scene! Scientist must be able to RECOGNIZE evidence Must be able to COLLECT evidence Must be able to PRESERVE evidence Remember…garbage in, garbage out!

Approaching a Crime Scene

Securing and Isolating Crime Scene The first officer at the scene must… 1) offer medical assistance when needed and/or make an arrest 2) exclude all unauthorized personnel from scene (very hard!) 3) Call for assistance/backup 4) isolate area (tape, barricades) Must try to preserve and protect area as much as possible

Once Secured… Lead investigator evaluates area Determines boundaries Establishes perpetrator’s path (entry and exit) Obvious evidence documented and photographed Initial walk-through & develop strategy for examination

Recording the Scene Limited time to work in CS in untouched state Records useful for investigation/court What are some methods of recording the crime scene?

Recording the Crime Scene Photographs Sketches Notes

PHOTOGRAPHY Take unaltered! Do not move evidence until picture is taken! If moved, must be recorded in notes All photos must show position and location to crime scene Close ups of smaller items must be taken Use a ruler or scale to note size Videotaping???

Photography Evidence Scene Close ups Perspectives Multiple angles Multiple views Entrances Exits Windows

Sketches After photographing…make a rough sketch Drawn at crime scene Contains accurate depictions of dimensions of scene (use tape measurer) Shows location of all objects having bearing on the case

Finished Sketch Done carefully, attention to appearance Must reflect rough sketch (admissible in court) Computer Aid Drafting (CAD) -software for reconstructing Drawn to scale

Rough Sketch to Final bsapp.com

Rough vs Finished Sketch

Notes Match to sketch Constant activity Quick, short, bulleted What can you not see from the photo? Helpful for long-term cases - memory Identifies all evidence – what is it? Who collected? Tape recording used sometimes

What should be noted? These notes must identify: Time an item of physical evidence was discovered Who discovered it? How and by whom it was packaged and marked Disposition of an item after it was collected May be the only source of information for refreshing one’s memory

The Search – Part 1 The search for physical evidence at a crime scene must be thorough and systematic. The search pattern selected will normally depend on the size and locale of the scene and the number of collectors participating in the search. For a factual, unbiased reconstruction of the crime, the investigator—relying upon his or her training and experience—must not overlook any pertinent evidence. Physical evidence can be anything from massive objects to microscopic traces.

Search Patterns

The Search – Part 2 Often, most evidence is clearly visible, BUT… Others can only be detected via examination in the lab Must collect ALL possible carriers of trace evidence Clothing Vacuum sweepings Rug samples Fingernail scrapings

Beyond the Crime Scene Search for evidence must extend to autopsy room Medical examiner – determine COD Tissues and organs retained for pathological and toxicological examination Medical examiner secures a variety of items for investigator

Evidence the ME sends to Investigator Victim’s clothing Fingernail scrapings Head and pubic hairs Blood (for DNA analysis) Vaginal, anal, and oral swabs (sex-related crimes) Recovered bullets from body Hand swabs from shooting victims (GSR)

Interactive Autopsy Assignment Go to this website and answer questions (given) http://www.hbo.com/autopsy/interactive/ Click on Interactive Autopsy to the right of the screen

Collecting & Packaging Evidence Goal: handle evidence so that there is least amount of change from CS to lab Potential problems Contamination Breakage Evaporation Accidental scratching/breaking Loss via carelessness Integrity = evidence kept intact (ex. Hair, soil should be left on clothing)

If evidence is found on large structure (door, wall)… remove specimen with forceps With blood, scrape off surface, transfer to moistened swab, or cut out area bearing stain

Most Important Point About Evidence Collection Each different item or similar items collected at different locations must be placed in separate containers! Prevents damage through contact Prevents cross contamination

Collecting Evidence Bag & Tag

Tools for Evidence Collection Forceps (to pick up small items) Unbreakable plastic pill bottles w/ pressure lids Hairs, glass, fibers, other small trace evidence Manila envelopes, screw-cap glass vials, metal/cardboard pill boxes also good for trace evidence

Small trace evidence and miscellaneous evidence Ordinary mailing envelopes should be avoided Druggist folds are often used for small trance Folding paper to produce closed container, keeping specimen inside Sealable plastic bags often universal container

2 Exceptions to the Rule Bloodstained materials Do NOT store in airtight containers! Moisture builds up and allows for mold growth Destroys evidentiary value of blood Use breathable paper envelopes or bags All clothing must be air dried and placed individually in separate bags Charred debris from a fire MUST be placed in airtight container to prevent evaporation of volatile petroleum residues

Chain of Custody Chain of Custody = a list of all people who came into possession of an item of evidence Must be established for use in court Everyone must be accounted for! Each person must obtain written record of acquisition and disposition Each person may be required to testify in court If not, authenticity and integrity of evidence is lost

Collecting Standard/Reference Samples Standard/Reference Sample: Physical evidence whose origin is known, such as blood or hair from a suspect, that can be compared to crime-scene evidence Can also be obtained from victim Paint from a hit-and-run vehicle

Other Controls Buccal Swab – swab from the inner portion of the cheek, performed to collect cells for use in determining the DNA profile of an individual Substrate Control Uncontaminated surface material close to area where physical evidence has been deposited Used to ensure that the surface on which a sample has been deposited does not interfere with lab results Used in arson cases – has surface been exposed to accelerant?

Submit Evidence to Lab Delivered personally or by mail depending on case and urgency Person familiar with case Can’t ship certain chemicals/live ammo/explosives Need evidence submission form Nature of crime, victim, case#, agency, investigator Brief description of case List of evidence What to investigate for each time

Evidence Submission Form

Murder Scene: Death and Autopsies Questions a forensic pathologist may ask: Who is the victim? What injuries are present? When did the injuries occur? How and why were injuries produced? Determining COD is primary role. If not known externally, AUTOPSY is performed: Medical dissection post-mortem to determine COD.

Review on Estimating TOD Rigor Mortis: Post mortem condition that results in the stiffening of muscle mass Manifests within 1st 24 hours; disappears within 36 hours Livor mortis: Post mortem condition that results in the settling of blood in areas closest to ground Skin appears blue/purplish Begins immediately after death and continues for up to 12 hours after death Was the victim’s position changed after death?

Review on estimating TOD Algor Mortis: Process by which the body temperature continually cools after death until it reaches the ambient temperature Beginning about 1 hour post mortem, body loses 1-1.5 degrees F per hour Rate of heat loss depends on… Location of body Size of body Victim’s clothing Weather condition

Another way to determine TOD Determine potassium (K+) levels in the ocular fluid in the eye (aka vitreous humor) After death, cells in the inner surface of eyeball release K+ into ocular fluid Use rate of release of K+ to determine TOD Also…food in stomach = last meal

Forensic Anthropology Identification of human skeletal remains Bones are extremely durable and undergo slow breakdown Provide individual characteristics: sex, age, race, injury Create facial reconstruction – to help ID Help ID in mass disaster

Forensic Anthropology

Forensic Entomology