Crime Scene Investigation Forensic Science Crime Scene Team

Crime Scene Investigation Forensic Science

Crime Scene Team • Police Officers (First Responders) • • Usually first at scene Secure Scene • District Attorney (possibly) • Sometimes present to determine if a search warrant is needed for crime-scene investigators • Crime-Scene Investigators • Document crime scene in detail and collect evidence • Recorders, sketch artists, photographers, evidence collectors • Medical Examiners (Also known as coroners) • May be present to determine the cause of death if a homicide or “possible” homicide occurred. • Detectives • Look for leads • • Interview witnesses Converse with CSI’s about evidence • Forensic Specialists • Certain crime scenes may call for experts in certain areas to be on scene • Example - entomologists

7 S’s of Crime Scene Investigation • Securing the Scene • Responsibility of first-responding police officer (first responder) • • others may assist as they arrive Safety of all individuals is FIRST priority Preservation of evidence is SECOND priority • • • First Responder = First person @ crime scene Tape off the area Restrict all unauthorized persons from entering Transfer, loss, or contamination of evidence can occur if the area is left unsecured Log kept of all those that visit crime scene Forensic experts (besides CSI) may be called in under certain circumstances

7 S’s of Crime Scene Investigation • Separating the Witnesses • Witnesses should not be allowed to talk to each other • Otherwise could lead to collusion • Witnesses working together to create a story • Accounts of witnesses will be compared later • Are accounts the same or different • Do accounts match up with FORENSIC EVIDENCE? • The following questions should 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/crime scene?

7 S’s of Crime Scene Investigation • Scanning the Scene • Determination of Primary Crime Scene and Secondary Crime Scene • Primary Crime Scene = location where initial crime took place • Example- Robbery site of a bank or store • Secondary Crime Scene = location other than primary crime scene where evidence may be found • Example- Home of a suspect in robbery • Determine where photos should be taken • Overall and up close of evidence

7 S’s of Crime Scene Investigation • Searching for Evidence • crime scene should be walked and location evidence marked. • • Grid Linear Quadrant or Zone Spiral • Xxx • Xx • xx

7 S’s of Crime Scene Investigation • Seeing (photographing) the Scene • Photos of overall crime scene from several angles • Initial • Close up photos of evidence (including bodies) with and without a measuring ruler • After crime scene has been searched and evidence marked • Triangulation of stationary objects should be included in photos as reference points • Distance and location of evidence from stationary reference points • Example: location and distance of murder weapon from oak tree.

7 S’s of Crime Scene Investigation • Securing and Collecting Evidence • ALL evidence needs to be properly packaged, sealed, and labeled • Protocol for packaging certain types of evidence exists to preserve evidence • Example- Most biological evidence must be place in breathable container so it can dry out (prevents mold) • Evidence then can be placed in paper bindle and then sealed in a plastic container or paper bag

7 S’s of Crime Scene Investigation • Securing & Collecting Evidence • Paper Bindle- a folded paper used to hold trace evidence 1. 2. 3. 4. 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

Maintaining Chain of Custody- the documented 2. and unbroken transfer of evidence Evidence should never be unattended 3. Document each time evidence opened Sign over to a lab technician Open bag on non-sealed edge Return items to the evidence bag Seal evidence bag in another 1. Bag the evidence bag Add identification Sign the evidence log Seal it Sign it across the sealed edge

Example of Evidence Inventory Label • Include: Case #, Inventory #, Description of evidence

Analysis of Evidence • Performed by forensic lab technicians • Usually very specialized • Example- DNA specialist, blood specialist ect… 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

7 S’s of Crime Scene Investigation • Sketching the Crime Scene • An accurate rough sketch of the crime scene is made, noting the position of the body (if any) and any other evidence • All objects (evidence) should be measured from two immovable landmarks (reference points) • • Direction of “North” should be labeled on sketch Includes other objects (doors, chairs, windows, furniture ect…) • A Final sketch should be made for possible presentation in court • • Drawn to scale (example 1/4 inch = ? Feet) Computer programs are available to create neater and nicer sketch for court proceedings

7 S’s of Crime Scene Investigation • Example of Sketch Format • Case number, date, location, and sketcher’s name should be included on rough and final sketch

Types of Evidence

Types of Evidence • Direct Evidence: includes first hand observations such as eyewitness account or police dashboard video cameras. • Example: Eyewitness, Photos, Video Tape

Types of Evidence • Circumstantial Evidence: is indirect evidence that can be used to imply a fact but that does not directly prove it. No one, other than the suspect and victim, actually sees when circumstantial evidence is left at the crime scene. This evidence can be physical or biological in nature. • Example: finding a gun at the suspect’s house, bloody knife, fingerprints, etc.

Trace Evidence • Trace evidence is a type of circumstantial evidence in which one object comes in contact with another object. • Known as Locard’s Exchange Principal • Examples: • Animal or Human Hair • Fingerprints • Soil of Plant Material (Pollen) • Body Fluids (Mucus, semen, saliva, or blood) • Fiber or debris from clothing • Paint Chips, broken glass, chemicals

Types of Circumstantial Evidence • Physical: Evidence not from living organisms Examples: impressions such as fingerprints, footprints, shoe prints, tire impressions, and tool marks, gun, knife, car(not paint), pan. Biological: From living organisms Examples: body fluids, hair, plant parts, and natural fibers.

Classifications of Evidence • Class Evidence: narrows an identity to a group of persons or things. Knowing the ABO blood type of a sample of blood type that may have been there, excludes others. • Individual Evidence: narrows an identity to a single person or thing. Individual evidence typically has such a unique combination of characteristics that it could only belong to one person or thing, such as a fingerprint.

Legal Considerations at the Crime Scene • All removal of evidence from a person or from the scene must conform to the Fourth Amendment: The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no warrants shall issue, but upon probable cause, supported by oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.

Warrantless Searches • Existence of emergency situations • Prevent the immediate loss or destruction of evidence • Search of a person or property following a lawful arrest • Search by consent

Mincey v. Arizona • After a homicide, police searched a scene for four days. Evidence collected was found to be inadmissible in court because the court did not feel that evidence would have been lost or destroyed in the time needed to obtain a legal search warrant.

Michigan v. Tyler • Fire destroyed a building and evidence was collected the first day at the scene. After the initial entry, later entries into the building produced evidence. All evidence from later entries to the property were deemed inadmissible in court.