Crime Scene Investigation and Evidence Collection Lecture Credits: Anthony (Bud) Bertino Goal to recognize, document and collect evidence at a crime scene
Sherlock Holmes» Sir Arthur Conan Doyle in the name of Sherlock Holmes helped refine our approach to scientific thinking by stating:» Look for the possible alternative first and then rule it out, if necessary.» Never guess but base your thinking on evidence» Devote your time to searching for answers to your question» Singularity is almost always a clue.» Logic and deductions can be applied to all crimes.» When you have eliminated the impossible, whatever remains, however improbable is the truth 2
Locard s Principle Principle of Exchange Part 1: when a person comes into contact with an object or another person, a cross transfer of physical evidence can occur
Part 2: the intensity, duration and nature of materials in contact determine the extent of transfer leading to trace evidence on the individuals and objects cross exchange bears as a silent witness identified an attacker based on trace evidence underneath victim s fingernail
Types of Evidence Direct Circumstantial: indirect evidence firsthand observations: -eyewitness accounts -dashboard video cameras -confessions Physical: - used to imply but prove a fact - may link a suspect and a crime scene ex. Suspect s gun found at crime scene Impressions, Fibers, weapons, bullets, shell casings reduces number of suspects to group Biological : may make group of suspects very small or even one individual Body fluids, hair, plant parts, natural fibers
Class evidence: narrows the identity to a group ex. Blood type ABO Individual evidence: single person, DNA, fingerprint, combination of unique traits
The Silent Witness - Trace Evidence» A crime has been committed. The deed is done. Out of sight and hearing of everyone. Edmund Locard was the first to formally state the principle of exchange 7
Trace evidence: Pet hair on clothes or rugs Hair on brush Fingerprints on glass Soil tracked inside on shoes Drop of blood on t shirt A used facial tissue Paint chips Broken glass Fiber from clothing
Crime Scene Investigation Team: Police Officers: usually first (possibly a DA for a search warrant) Crime Scene Investigators: document crime and collect physical evidence Recorder Sketch artist Photographers Evidence collectors Medical Examiners: coroners may be necessary to determine cause of death in a homicide case Detectives: look for leads, interview witnesses and talking to the CSI about evidence Specialists: entomologists, psychologists
7 S s of CSI 1. Securing the Scene 2. Separating the Witnesses 3. Scanning the Scene 4. Seeing the Scene 5. Sketching the Scene 6. Searching for Evidence 7. Securing and Collecting the Evidence
Securing the Scene First responding officer s job #1 SAFETY #2 Preserve evidence Protect area Limit exchange Request team
Separating the Witnesses 3rd priority; try to prevent collusion Ask the following questions: 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?
Scan the scene to determine what photos are needed May determine primary and secondary crime scene
Seeing the Scene Photos of overall area Close up photos with and without rulers Triangulation of stationary objects should be included in the photos as reference point View needs to be taken from several different angles and distances Several close up photos of evidence and bodies
http://www.ncit.com/tips Tricks/Sketching/sketching.html http://www.authentegrity.com/download/crime_scene_diagramming.pdf accurate rough sketch is made noting position of body if applicable and any other evidence All objects should be measured from 2 immovable landmarks Label N on the sketch and a scale Any objects within the vicinity of crime scene: windows, furniture, doors. Outside; position of trees, vehicles, shrubs. Make another final sketch for court Sketching the Scene:
Searching for Evidence Depends on number of investigators Walk the scene marking location of evidence, photo, sketch Single investigator: use grid, linear or spiral Group: linear, zone or quadrant pattern Patterns are systematic to ensure no area is left unsearched Additional light for hair / fibers Vacuum cleaner Flashlight and forceps reduce picking up extraneous
Securing and Collecting the Evidence Must be properly packaged, sealed and labeled Specific procedures must be followed for collection and storage Liquids and arson remains = airtight, unbreakable container Biological evidence: breathable containers to reduce mold
After evidence is allowed to dry then packaged into a paper bindle Paper bindle (druggist fold) then placed in paper or plastic container Outer container then sealed with tape and signed by the collector on the label
Evidence log and Chain of Custody document in attached to the evidence container. Contains Case number Item inventory number Description of the evidence Name of the suspect Name of the victim Date and Time of recovery Signature of person recovering evidence Signature of any witnesses present during collection
CHAIN OF CUSTODY : Must be maintained to secure evidence 1. Collector finds evidence and bags it in paper or plastic 2. The final container is the collection bag labeled with pertinent info 3. Seal and collector s signature written across sealed edge 4. Taken to a lab and signed over to technician 5. Tech opens bag (tears) somewhere not the sealed edge 6. Technician handles evidence then repackages evidence in original packaging and then seals in new packaging 7. Sign chain of custody log 8. Ensures responsible handling from crime scene to courtroom
Analyze Evidence FBI crime is largest forensics lab in the world Process all evidence to determine facts of the case Each technician has one specialty (one type of evidence) Lab results sent to lead detective Test results lead to crime scene reconstruction = hypothesis about sequence of events before crime to commission Detective takes evidence and tries fit into scenario Analysis can link a suspect to scene or victim or lead to acquittal Direct evidence is more compelling than circumstantial
Crime Scene Reconstruction Hypothetical sequence of events Exam evidence and compare to witness accounts to determine reliability Evidence does not lie but it can be staged
Staged Crime Scenes Unique problem: evidence does not match testimony Common situations: Arson: stage fire to cover robbery or murder Suicide/murder: death may alcohol or overdose Burglary: staged to collect rbbery, be money
Things to consider when determining staging occurred Initially treat all death investigations as homicide Do the type(s) of wounds found on the victim match the weapon employed? Could the wounds be easily self inflicted? Establish a profile of the victim through interviews with friends and family Evaluate the behavior ( mood and actions) of the victim before the event Evaluate the behavior ( mood and actions) of any suspects before the event Corroborate statements with evidential facts Reconstruct the event Conduct all forensic examinations to determine the facts of the case
SUMMARY Locard s principle Evidence may be direct: eyewitness or Circumstantial: does not directly prove a fact Evidence can be physical or biological (trace can be either) CSI team: police officers, detectives, CSI investigators, medical examiners and specialists CS investigation: recognizing, documenting and collecting evidence from a scene First responding officer: id extent of crime scene (including 1 and 2), secure the scene and segregate witnesses walk the scene, id evidence then document scene by photos and sketches Evidence must be properly handled, collected and labeled to maintain Chain of Custody Evidence is analyzed in a forensic lab, results provided to detectives who fit results into crime scenario