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

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

Principle of Exchange Established by Dr. Edmond Locard, the principle states: When a person comes in contact with an object or another person, a cross-transfer of physical material can occur Study of the material can determine the nature and duration of the transfer “Locard’s Exchange Principle” Forensic Science: Fundamentals & Investigations, Chapter 2

Types of Evidence Direct evidence Testimony by a witness about what that witness saw, heard, or did (Eyewitness Testimony – has probative value) Probative value: the ability of evidence to prove something that is material to a crime Forensic Science: Fundamentals & Investigations, Chapter 2

Types of Evidence Circumstantial evidence Physical evidence also called Indirect trace evidence Has PROBATIVE Value Physical evidence e.g., fingerprints Biological evidence e.g., blood or hairs Forensic Science: Fundamentals & Investigations, Chapter 2

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

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 Kendall/Hunt Publishing Company

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 Kendall/Hunt Publishing Company

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

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. (From Suspects and victim) (Found at the Crime scene) Kendall/Hunt Publishing Company

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

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

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

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

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

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) Fingerprints Blood DNA Typing Kendall/Hunt Publishing Company

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

. . . . . . . . . . . . . . Summary . . . . Locard’s exchange principle: Contact between people and objects can transfer material that can determine the nature and duration of the transfer Evidence can be direct or indirect Physical or biological traces A crime scene investigation team consists of police, detectives, crime scene investigators, medical investigators, and specialists. Forensic Science: Fundamentals & Investigations, Chapter 2

. . . . . . . . . . . . . . . . . Summary Investigations consist of recognizing, documenting, and collecting evidence. First responding officers identify the extent of the crime scene, secure it, and segregate witnesses. Crime scene investigators document the crime scene. Evidence is collected, packaged, and labeled. The evidence is analyzed and interpreted to fit the crime scenario. Forensic Science: Fundamentals & Investigations, Chapter 2