002 crimescenebasics - final (2).pptx hh
- 1. Forensic Science T. Trimpe 2006 http://sciencespot.net
- 2. CRIME SCENE: Any physical location in which a crime has occurred or is suspected of having occurred. Source: http://www3.sc.maricopa.edu/ajs/crime_scene_technician.htm PRIMARY CRIME SCENE: The original location of a crime or accident. SECONDARY CRIME SCENE: An alternate location where additional evidence may be found. ALIBI: Statement of where a suspect was at the time of a crime. ACCOMPLICE: Person associated with someone suspected of committing a crime. SUSPECT: Person thought to be capable of committing a crime. Crime Scene Vocabulary
- 3. Testimonial evidence includes oral or written statements given to police as well as court testimony by people who witnessed an event. Physical evidence refers to any material items that would be present at the crime scene, on the victims, or found in a suspect’s possession. Trace evidence refers to physical evidence that is found in small but measurable amounts, such as strands of hair, fibers, or skin cells. Source: http://www3.sc.maricopa.edu/ajs/crime_scene_technician.htm What will evidence collected at a scene do for the investigation? • May prove that a crime has been committed • Establish key elements of a crime • Link a suspect with a crime scene or a victim • Establish the identity of a victim or suspect • Corroborate verbal witness testimony • Exonerate the innocent. • Give detectives leads to work with in the case Types of Evidence
- 4. POLICE OFFICERS are typically the first to arrive at a crime scene. They are responsible for securing the scene so no evidence is destroyed and detaining persons of interest in the crime. The CSI UNIT documents the crime scene in detail and collects any physical evidence. The DISTRICT ATTORNEY is often present to help determine if any search warrants are required to proceed and obtains those warrants from a judge. The MEDICAL EXAMINER (if a homicide) may or may not be present to determine a preliminary cause of death. SPECIALISTS (forensic entomologists, anthropologists, or psychologists) may be called in if the evidence requires expert analysis. DETECTIVES interview witnesses and consult with the CSI unit. They investigate the crime by following leads provided by witnesses and physical evidence. Source: http://science.howstuffworks.com/csi.htm Crime Scene Personnel
- 5. Step 1: Interview The first step in investigating a crime scene is to interview the first officer at the scene or the victim to determine what allegedly happened, what crime took place, and how was the crime committed. This information may not be factual information but it will give the investigators a place to start. Step 2: Examine The second step in the investigation of a crime scene, which will help identify possible evidence, identify the point of entry and point of exit, and outline the general layout of the crime scene. Step 3: Document The third step in the protocol involves creating a pictorial record of the scene as well as a rough sketch to demonstrate the layout of the crime scene and to identify the exact position of the deceased victim or other evidence within the crime scene. Step 4: Process This is the last step in the protocol. The crime scene technician will process the crime scene for evidence, both physical and testimonial evidence. It is the crime scene technicians responsibility to identify, evaluate and collect physical evidence from the crime scene for further analysis by a crime laboratory. Crime Scene Protocol Adapted from http://www.feinc.net/cs-proc.htm
- 6. Kendall/Hunt Publishing Company 6 Top Reasons for Committing a Crime Money Revenge Emotion—love, hate, anger Source of Evidence Body Primary and/or Secondary Crime Scene Suspect(s)
- 7. Locard’s Exchange Principle States that with contact between two items, there will always be an exchange. This is the basis of trace evidence collection at a crime scene.
- 8. Physical Evidence Any object or material found As large as building, as small as hair…odor and submicroscopic like DNA Unique to crime Generally more reliable than testimony
- 9. Value of Physical Evidence Can prove crime was committed Support or reject witness testimony Link suspect with victim or crime scene Determine identity of people involved in crime Allows investigators to re-create crime
- 10. Individual Evidence Best type of evidence Anything that can be linked to a unique/individual source Ex: ◦ Fingerprints ◦ DNA pattern ◦ Handwriting ◦ Broken glass that fits together
- 11. Class Evidence Most evidence fits in this category Object has characteristics common to a group of objects Ex: ◦ Blue jeans ◦ Even despite the different sizes, shades, and brand ◦ there are still thousands of pairs just like them ◦ BUT – tears, stains, creases, patches can individualize them
- 12. Probative Value Definition: Ability of evidence to prove something that is material to crime ◦ Probative means supplying proof or evidence How can you increase probative value of class evidence??? ◦ Get as many different types of objects as possible to link the suspect to the crime or victim What’s the probative value of class evidence vs. individual evidence???
- 13. Step 1 The first officer to arrive at the scene is responsible for securing the crime scene. Priorities should be: 1.Medical assistance for individuals in need 2.Arresting the perpetrator 3.Protect crime scene 4.Exclude all unauthorized personnel from the scene. 5.Communicate to crime scene investigators all movements and alterations made to the scene.
- 14. Step 2 Preliminary Examination ◦ “Walk-through” Documenting the crime scene ◦ Videotaping, Photography, Sketches, and Notes are the four methods for crime-scene recording Ideally all four should be employed; however, as is often the case, personnel and monetary limitations may prohibit the utilization of some.
- 15. Photography Must be in an unaltered condition ◦ Overview photographs Unless there are injured parties involved, objects must not be moved until they have been photographed from all necessary angles. As items of physical evidence are discovered, they are photographed to show their position and location relative to the entire scene. ◦ Midrange photographs ◦ Close-ups photographs When the size of an item is of significance, a ruler or other measuring scale may be inserted and included as a point of reference.
- 16. Sketching in relation to Photography A sketch can: ◦ Depict entire scene in one visual whereas a photograph cannot ◦ Be selective & eliminate distracting confusion ◦ Record spatial relationship between items Sketches may give a better overall layout of the scene than do photos.
- 17. Types of Sketches Types of Sketches: ◦ **Overhead Most common, overhead view, type we will do ◦ Cross projection or exploded view Cut apart walls like a box & lay flat ◦ Elevation View from eye level ◦ Perspective 3D photograph-like
- 19. Sketches Rough Sketch —A draft representation of all essential evidence information and measurements are taken drawn at the crime scene Shows all recovered items of physical evidence Important features of the crime scene (entry, exits, etc) Finished Sketch —A precise rendering of the crime drawn to scale not normally completed at the crime scene drawn with care and concern for aesthetic appearance
- 21. Rough sketch should include: ◦ Preparer’s Name ◦ Date and Time ◦ Compass direction ◦ Objects/evidence ◦ Measurements of rooms, windows, doors & furniture ◦ Distances between objects, bodies, persons & entrances/exits ◦ Key/legend
- 22. Procedure for sketching Measure all distances ◦ inches used ◦ Measure walls, windows, door, furniture, people, guns, shoe prints, etc. Triangulation method: There are 3 points of measurement: item of evidence & 2 fixed objects Triangle is created when measurements are made from each of the 2 fixed points to item of evidence Rectangular Coordinate Measurements
- 24. Notes Must be a constant throughout the processing of the crime scene Should include: Detailed written description of the scene location of items of physical evidence recovered Time and by whom evidence was discovered How and by whom evidence was packaged May be the only way to refresh one’s
- 25. Importance of Recording Only a limited amount of time in untouched state Opportunity to record original state is key Important for: ◦ Investigation ◦ Presentation at a trial
- 26. Kendall/Hunt Publishing Company 26 SEARCH METHODS Line or strip method—best in large, outdoor scenes Grid method—basically a double-line search; effective, but time-consuming Zone method—most effective in houses or buildings; teams are assigned small zones for searching Wheel or ray method—best on small, circular crime scenes Spiral method—may move inward or outward; best used where there are no physical barriers
- 27. Search Methods
- 28. The Search Often, many items of evidence are clearly visible but others may be detected only through examination at the crime laboratory. ◦ For this reason, it is important to collect possible carriers of trace evidence, such as clothing, vacuum sweepings, and fingernail scraping
- 29. Autopsy Search for physical evidence must extend beyond the crime scene to the autopsy room ◦ The medical examiner or coroner ◦ examine the victim to establish a cause and manner of death ◦ Tissues and organs will be retained for 1. pathological examination 2. toxicological examination
- 30. Physical evidence collected from body ◦ Victim’s clothing ◦ Fingernail scrapings ◦ Hairs ◦ Blood (for DNA typing purposes) ◦ Body Swabs (in sex related crimes) ◦ Recovered bullets from the body ◦ Hand swabs from shooting victims(for gunshot residue analysis)
- 31. Packaging Evidence Each item collected at different locations must be placed in separate containers. 1. Prevents damage through contact and prevents cross-contamination. 2. Manilla envelopes, pill bottles, twist on cap glass bottles, paper (using “druggist fold”) Bloodstained materials stored in airtight containers may encourage the accumulation of moisture and the growth of mold, which can destroy the evidential value of blood. In these instances, wrapping paper, manila envelopes, or paper bags are recommended
- 32. Chain of Custody Chain of Custody—A list of all persons who came into possession of an item of evidence. ◦ Important for court ◦ Adherence to standard procedures is critical to chain of custody. 1. Recording the location of evidence 2. Marking it for identification 3. Properly completing evidence submission forms for laboratory analysis **Every person who handled or examined the evidence and where it is at all times must be accounted for.