Crime-Scene Investigation and Evidence Collection Chapter 2

Objectives 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. Summarize the seven 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. Describe how evidence from a crime scene is analyzed.

Crime Scene Investigation Goal: recognize, document, and collect evidence at the scene of a crime Piece together evidence to form a picture of what happened at the crime scene Ability to reconstruct the scene

Trace Evidence Small but measureable amounts of physical or biological material found at a crime scene Examples: pet hair on clothes or rugs, hair on your brush, fingerprints on a glass, soil tracked into a house on your shoes, drop of blood on a t-shirt, broken glass, etc. Physical transfer of trace evidence occurs when two people come in contact Dr. Edmond Locard (world’s first forensic lab in Lyon, France) was first to note this condition

Trace Evidence

Locard’s Exchange Principle 1. When a person comes into contact with an object or another person, a cross-transfer of physical evidence can occur Exchanged materials indicate that the two objects were in contact Trace evidence can be found on both persons (and/or objects) because of cross-transfer 2. Intensity, duration, and nature of the materials in contact determine the extent of the transfer i.e. fistfight vs. brushing past another person

Types of Evidence Direct Evidence Circumstantial Evidence Includes firsthand observations Ex: eyewitness accounts/testimony, police dashboard video cameras, confessions Circumstantial Evidence Implies a fact but does not directly prove it Links crime scene to a suspect Trace evidence Physical or biological Ex: finding a suspect’s gun at the site of a shooting

Circumstantial Evidence Physical Evidence Impressions – fingerprints, footprints, shoe prints, tire impressions, tool marks Fibers, weapons, bullets, shell casings Typically reduces the number of suspects to a specific, smaller group of individuals (exception?) Biological Evidence Body fluids, hair, plant parts, natural fibers May make the group of suspects very small or reduce it to a likely individual More persuasive in court

Types of Evidence Class Evidence Individual Evidence Narrows an identify to a group of persons or things and excludes others Ex: ABO blood type Individual Evidence Narrows an identity to a single person or thing Ex: unique combination of characteristics, such as a fingerprint

CSI Team Police officers Crime-scene investigators Typically first to arrive Crime-scene investigators Document scene, collect physical evidence Recorders, sketch artists, photographers, evidence collectors Medical examiners (coroners) Determine cause of death Detectives Interview witnesses, talk to crime-scene investigators about evidence Specialists Consulted if evidence requires their expertise

Seven S’s of CSI Securing the scene Separating the witnesses Scanning the scene Seeing the scene Sketching the scene Searching for evidence Securing and collecting evidence

Securing the Scene Police officer = First responder First priority: safety Determine need for medical assistance. Second priority: preservation of evidence Restrict unauthorized entry – security log of all who visit Locard’s exchange principle Protect from the elements!

Separating the Witnesses Avoid collusion (working together to create a story) Altering eyewitness testimony Questions to be asked: When did the crime occur? Who called in the crime? Who is the victim? Can the perpetrator be identified? What did you see happen? Where were you when you observed the crime scene?

Scanning the Scene Where should photos be taken? Primary crime scene – where the crime took place Secondary crime scene – location other than primary scene where evidence is found

Seeing the Scene Photography! Overall view photographs Items-of-evidence photographs Close-up views with and without a measuring ruler Triangulation of stationary objects included as reference points Several different angles and distances

Sketching the Scene Rough sketch Final sketch Notes position of body and other evidence Objects measured using two immovable landmarks Direction should be labeled and scale of distance provided Other objects in vicinity of crime scene should be included Final sketch Typically to scale Neater! Easier to read Often on computer Used in court proceedings

Sketching the Scene

Searching for Evidence Systematic pattern for searching so no area goes unsearched Single Investigator: search in grid pattern, linear pattern, or spiral pattern Group of Investigators: linear pattern, zone pattern, quadrant pattern Materials needed: additional light sources/flashlight for examination for trace evidence, forceps for collecting evidence Oblique lighting! Practice

Searching for Evidence

Securing and Collecting Evidence Specific procedures and techniques based on type of evidence Ex: liquids and arson in airtight, unbreakable containers, biological evidence in breathable containers to aid in drying and reducing mold FBI and state police agencies publish descriptions of proper procedures for storing and collecting evidence Paper bindle: holds biological evidence that has been air dried Also called a “druggist’s fold” Placed in plastic or paper container which is sealed with tape and labeled with signature of collector across the tape Evidence log and chain of custody document attached to container

Packaging Evidence Size of bindle depends on size of evidence (sheet of paper vs. large sheet of wrapping paper, etc.) Large wet objects should be placed in paper container and sealed to allow to air dry and never packaged in plastic while wet! DNA can degenerate and evidence can become moldy Control samples must be obtained from the victim for the purpose of exclusion

Packaging Evidence Steps to packaging evidence Choose appropriate-size sheet of clean paper Crease the paper into nine sections Place evidence in center Fold left and right sides in Fold in top and bottom Insert top flap into bottom flap and tape closed Place bindle inside plastic or paper evidence bag and fold bag closed. Place a seal over folded edge of evidence bag Collector writes his or her name over the folded edge

Evidence Log Case number Item inventory number Description of evidence Name of suspect Name of victim Date and time of recovery Signature of person recovering evidence Signature of any witnesses present during collection

Chain of Custody Final container for evidence is sealed and the collector’s signature is written across the sealed edge Anyone who comes in contact from that point forward must sign the chain of custody form When opened in the lab, it is opened at a location other than the sealed edge Repackage in original packaging, resealed in new packaging with signature, and signs chain of custody

Chain of Custody Practice! 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

Analysis of Evidence Forensic lab technicians are specialized and process one type of evidence at a crime lab Evansville Crime Lab Lead detective receives laboratory results End goal: crime-scene reconstruction Lab results can: Show reliability of witness accounts Establish the identity of suspects or victims Show suspects to be innocent (exclude them) or link them with a scene or victim

Crime Scene Reconstruction Forming a hypothesis of the sequence of events from before the crime was committed through its commission Compare evidence with witnesses’ statements and figure out how it all fits together Maintain an open mind…why?

Staged Crime Scenes Perpetrator makes the scene look like something it’s not Lab results don’t match up with testimony of witnesses Common examples: Arson – staging a fire to cover up another crime Suicide/murder Burglary – staging to collect insurance money

Staged Crime Scenes Initially treat all death investigations as homicides 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? Corroborate statements with evidential facts Reconstruct the event Conduct all forensic examinations to determine the facts of the case

Case #1 – JonBenet Ramsey Found dead in the basement of her home 12/26/96. Mother called 911 to say she was missing and that a ransom note was found. Mistakes: didn’t search the house for 7 hours post- 911 call, only blocked off JonBenet’s bedroom, father found her in basement and covered her with a blanket and moved her to the living room, didn’t separate witnesses (parents) and get full statements, did not secure the house, pathology didn’t examine body for 18 hours after crime Still unsolved! Maybe we will find out more on Dr. Phil on September 12?! Or CBS on September 18?

Case #2 – OJ Simpson People vs. OJ 7:24-9:35 15:23-17:53 Simpson’s defense poked major holes in the LAPD’s forensic investigation processes that has led to changes in protocol. This is argued as the reason to which OJ Simpson was acquitted. Documentation.  In 1994, the crime lab did not routinely document its handling of the evidence.   Chain of Custody.  During the Simpson trial, there was a great deal of evidence that prosecution sought to produce at trial.  However, the source of that evidence was recorded and could not be explained.

Case #2 – OJ Simpson Careful Examination of Evidence.  During the OJ murder investigation, no one noticed any blood on a pair of socks that were collected from Simpson’s bedroom until two months later when the socks were examined in the crime lab.  Defense experts suggested at trial that the blood was smeared on the socks while they were lying flat, not while someone was wearing them. Proper Evidence Handling.  Forensic technicians were criticized for improperly packaging evidence samples and leaving them in a hot van on a summer day.  A rookie technician had collected most of the evidence in the 1994 murder case.   Contamination of Evidence.  In 1994, a police detective took a blood sample from Simpson, and then carried the vial of Simpson’s blood in his pocket, back to the crime scenes.  At trial, the defense suggested that the blood was brought back to the crime scene for the purposes of planting that evidence at the scene.