Forensic Science: Fundamentals & Investigations, Chapter 2 1 Chapter 2 Crime Scene Investigation and Evidence Collection By the end of this chapter you will be able to: o Summarize Locard’s exchange principle o Identify four examples of trace evidence o Distinguish between direct and circumstantial evidence o Identify the type of professionals who are present at a crime scene o Describe how evidence from a crime scene is analyzed All Rights Reserved South-Western / Cengage Learning © 2012, 2009

Forensic Science: Fundamentals & Investigations, Chapter 2 2 Chapter 2 Crime Scene Investigation and Evidence Collection By the end of this chapter you will be able to: o Summarize the three steps of a crime scene investigation o Explain the importance of securing the crime scene o Identify the methods by which a crime scene is documented o Demonstrate proper technique in collecting and packaging trace evidence

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4 Principle of Exchange “Locard’s Exchange Principle” o When a person comes in contact with an object or another person, a cross-transfer of physical material can occur o Study of the material can determine the nature and duration of the transfer

Forensic Science: Fundamentals & Investigations, Chapter 2 5 Types of Evidence Direct evidence: Testimony by a witness about what they saw, heard, or did

6 Types of Evidence Circumstantial evidence also called Indirect trace evidence Physical evidence e.g., fingerprints Biological evidence e.g., blood or hairs

Forensic Science: Fundamentals & Investigations, Chapter 2 7 Types of Evidence Explain why this would be or would not be trace evidence

8 Reliability of Eyewitness (Direct Evidence – Testimonial Evidence) Factors:  Nature of the offense and the situation in which the crime is observed  Characteristics of the witness  Manner in which the information is retrieved Additional factors:  Witness’s prior relationship with the accused  Length of time between the offense and the identification  Any prior identification or failure to identify the defendant  Any prior identification of a person other than the defendant by the eyewitness

9 Eyewitness  A police composite may be developed from the witness testimony by a computer program or forensic artist.  “Perception is reality.”  As a result of the influences in eyewitness memory, physical evidence becomes critical. Faces—a composite program by InterQuest

10 Value of Physical Evidence  Generally more reliable than testimonial  Can prove that a crime has been committed  Can corroborate or refute testimony  Can link a suspect with a victim or with a crime scene  Can establish the identity of persons associated with a crime  Can allow reconstruction of events of a crime

Kendall/Hunt Publishing Company 11 Reconstruction Physical Evidence is used to answer questions about:  what took place  how the victim was killed  number of people involved  sequence of events A forensic scientist will compare the questioned or unknown sample with a sample of known origin. (Found at the Crime scene) (From Suspects and victim)

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Kendall/Hunt Publishing Company 13 Types of Physical Evidence  Transient Evidence—temporary; easily changed or lost; usually observed by the first officer at the scene  Pattern Evidence—produced by direct contact between a person and an object or between two objects  Conditional Evidence—produced by a specific event or action; important in crime scene reconstruction and in determining the set of circumstances or sequence within a particular event  Transfer Evidence—produced by contact between person(s) or object(s), or between person(s) and person(s)  Associative Evidence—items that may associate a victim or suspect with a scene or each other; ie, personal belongings —Lee and Labriola in Famous Cases, 2001

Kendall/Hunt Publishing Company 14 Examples of Transient Evidence  Odor—putrefaction, perfume, gasoline, urine, burning, explosives, cigarette or cigar smoke  Temperature—surroundings, car hood, coffee, water in a bathtub, cadaver  Imprints and indentations— footprints, teeth marks in perishable foods, tire marks on certain surfaces  Markings

Kendall/Hunt Publishing Company 15 Examples of Pattern Evidence Pattern Evidence—most are in the form of imprints, indentations, striations, markings, fractures or deposits.  Clothing or article distribution  Gun powder residue  Material damage  Body position  Tool marks  Modus operandi (M.O.)  Blood spatter  Glass fracture  Fire burn pattern  Furniture position  Projectile trajectory  Tire marks or skid marks

Kendall/Hunt Publishing Company 16 Examples of Conditional Evidence  Light—headlight, lighting conditions  Smoke—color, direction of travel, density, odor  Fire—color and direction of the flames, speed of spread, temperature and condition of fire  Location—of injuries or wounds, of bloodstains, of the victim’s vehicle, of weapons or cartridge cases, of broken glass  Vehicles—doors locked or unlocked, windows opened or closed, radio off or on (station), odometer mileage  Body—position, types of wounds; rigor, livor and algor mortis  Scene—condition of furniture, doors and windows, any disturbance or signs of a struggle

Kendall/Hunt Publishing Company 17 Classification of Evidence by Nature  Biological—blood, semen, saliva, sweat, tears, hair, bone, tissues, urine, feces, animal material, insects, bacterial, fungal, botanical  Chemical—fibers, glass, soil, gunpowder, metal, mineral, narcotics, drugs, paper, ink, cosmetics, paint, plastic, lubricants, fertilizer  Physical—fingerprints, footprints, shoe prints, handwriting, firearms, tire marks, tool marks, typewriting  Miscellaneous—laundry marks, voice analysis, polygraph, photography, stress evaluation, psycholinguistic analysis, vehicle identification

Kendall/Hunt Publishing Company 18 Evidence Characteristics  Class—common to a group of objects or persons (low probative value-can help to prove something)  Individual—can be identified with a particular person or a single source (high probative value) Blood DNA Typing Fingerprints

Kendall/Hunt Publishing Company 19 Class vs Individual Evidence Which examples do you think could be individual evidence? Does class evidence help to prove anything? “the value of class evidence”

Kendall/Hunt Publishing Company 20 Class vs Individual Evidence  The large piece of glass fits to the bottle—it is individual evidence  These fibers are class evidence—there are millions like them.

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Forensic Science: Fundamentals & Investigations, Chapter 2 22 The Crime Scene Investigation Team Who is at the crime scene? o Police and o District attorney (possibly) o Crime scene investigators o Medical examiners o Detectives o Specialists

Forensic Science: Fundamentals & Investigations, Chapter 2 23 The Seven S’s of Crime Scene Investigation 1. Secure the scene (Seek Medical Attention 1 st Preserve evidence 2 nd ) 2. Separate the witnesses 3. Scan the scene (Detailed observ. & notes) 4. Seeing the scene (Photographs) 5. Sketch the scene (Rough & Final Sketch) 6. Search for evidence 7. Secure the collected evidence ** See additional notes/activities**

Forensic Science: Fundamentals & Investigations, Chapter 2 24 Crime-Scene Sketch Form

Forensic Science: Fundamentals & Investigations, Chapter 2 25 Crime-Scene Search Patterns Pattern used depends on: Number of investigators & size of area Single investigator – grid, linear or spiral Group of investigators – linear, zone or quadrant Patterns are systematic and ensures that no area is left unsearched

Forensic Science: Fundamentals & Investigations, Chapter 2 26 Packaging the evidence 1. Crease a clean paper and place evidence in the X position 2. Fold in the left and right sides, and then fold in the top and bottom 3. Put the bindle into a plastic or paper evidence bag affixing a seal over the opening 4. Write your name on the seal

Forensic Science: Fundamentals & Investigations, Chapter 2 27 Evidence ID Forms

Forensic Science: Fundamentals & Investigations, Chapter 2 28 Chain of Custody Maintaining a chain of custody log is essential to present credible evidence in court

Forensic Science: Fundamentals & Investigations, Chapter 2 29 Chain of Custody (cont’d.) 1. Bag the evidence Add identification Seal it Sign it across the sealed edge 2. Sign over to a lab technician Open bag on non-sealed edge 3. Return items to the evidence bag Seal evidence bag in another bag Sign the evidence log

Forensic Science: Fundamentals & Investigations, Chapter 2 30 Analyze the Evidence o Facts result from collected evidence processed by the forensic lab o Lead detective aims to see how facts fit into the crime scenario

Forensic Science: Fundamentals & Investigations, Chapter 2 31 Analyze the Evidence Lab results can: o Show reliability of witness accounts o Establish the identity of suspects or victims o Show suspects to be innocent or link them with a scene or victim

Forensic Science: Fundamentals & Investigations, Chapter 2 32 Crime Scene Reconstruction Crime scene reconstruction involves: o Forming a hypothesis of the sequence of events o From before the crime was committed through its commission o Means? Motive? Opportunity?

Forensic Science: Fundamentals & Investigations, Chapter 2 33 Staged Crime Scenes When lab results don’t match up with the testimony of witnesses Common examples: o Staging a fire—to cover bankruptcy o Staging a suicide—to cover a murder o Staging a burglary—to collect insurance money

Forensic Science: Fundamentals & Investigations, Chapter 2 34 Staged Crime Scenes Was the crime scene staged? Consider: o Does the type of wound match the weapon? o Could the wound be easily self-inflicted? o What were the mood and actions of the victim before the event? o What were the mood and actions of the suspect before the event?

Forensic Science: Fundamentals & Investigations, Chapter Summary Summary.... o Locard’s exchange principle: Contact between people and objects can transfer material that can determine the nature and duration of the transfer o Evidence can be direct or indirect Physical or biological traces o A crime scene investigation team consists of police, detectives, crime scene investigators, medical investigators, and specialists.

Forensic Science: Fundamentals & Investigations, Chapter Summary Summary o Investigations consist of recognizing, documenting, and collecting evidence. o First responding officers identify the extent of the crime scene, secure it, and segregate witnesses. o Crime scene investigators document the crime scene. o Evidence is collected, packaged, and labeled. o The evidence is analyzed and interpreted to fit the crime scenario.