Unit 2 Crime Scene Investigation and Evidence

Objectives For Unit 2 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 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 describe how evidence from a crime scene is analyzed

CRIME SCENE: Any physical location in which a crime has occurred or is suspected of having occurred. 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

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. Crime Scene Personnel

Principle of Exchange Dr. Edmond Locard, director of the world’s first forensic lab (1910, Lyon, France), established the idea of the exchange principle; namely that: 1. When a person comes in contact with an object or another person, a cross-transfer of physical material can occur. 2. Study of the material can determine the nature and duration of the transfer.

Types of Evidence Statements of a witness in court would be direct evidence. Indirect or circumstantial evidence, such as a fingerprint (physical evidence) or blood or hairs (biological evidence), would imply something, and is called trace evidence.

Physical Evidence Crime Laboratories run on physical evidence Physical evidence encompasses any and all object that can establish that a crime has been committed or can provide a link between a crime and its victims or a crime and its perpetrator But if physical evidence is to be used effectively for aiding the investigator, its presence first must be recognized at the crime scene.

Types of Evidence Evidence taken from a crime scene. Direct or circumstantial evidence? Physical or biological evidence?

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: 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

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

The Crime Scene Investigation Team Who is at the crime scene  Police and possibly a district attorney  Crime scene investigators  Medical Examiners  Detectives  Specialists

The Seven S’s of a Crime Scene Secure the scene Separate the witness Scan the scene See to it the crime scene examiners receive overall and close up photos with and without measuring rulers Sketch the scene Search for evidence Secure the collected evidence

The 1 st Step The first officer to arrive at the scene is responsible for securing the crime scene  Priorities should: Medical assistance for individuals in need Arresting the perpetrator Exclude all unauthorized personnel from the scene.

The 1 st Step Once the scene is secured, the preliminary exam must begin Recording the crime scene becomes a critical piece to the investigation process

Recording Methods Photography, Sketches, and notes are the three methods for crime-scene recording Ideally all three should be employed; however, as is often the case, personnel and monetary limitations may prohibit the utilization of some

Photography The most important prerequisite for photographing a crime scene is for it to be in an unaltered condition 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.

Photography After these overviews of the crime scene are taken close-ups should be taken to record detail When the size of an item is of significance, a ruler or other measuring scale may be inserted near the object ad included in the photograph as a point of reference

Sketches Next Sketches of the scene are made  Rough Sketch – A draft representation of all essential information and measurements at the crime scene. This sketch is drawn at the crime scene. It shows all recovered items or physical evidence, as well as other important features of the crime scene.  Finish sketch – A precise rendering of the crime scene, usually drawn to scale. This type is not normally completed at the crime scene Unlike the rough sketch, the finished sketch is drawn with care and concern for aesthetic appearance.

Notes Note taking must be a constant activity throughout the processing of the crime scene These notes must include a detailed written description of the scene with the location of items of physical evidence recovered

Notes The notes must identify  The time an item of physical evidence was discovered  By whom it was discovered  How and by whom it was packaged and marked  The disposition of the item after it was collected The note taker has to keep in mind that this written record may be the only source of information for refreshing one’s memory

Recording the Crime Scene Investigators have only a limited amount of time to work a crime site in its untouched state The opportunity to permanently record the scene in its original state must not be lost Every step of the investigation should be documented thoroughly with an appropriate method

The Preliminary Exam A lead investigator starts the process of evaluating the area.  1 st the boundaries of the scene must be determined  Followed by the establishment of the perpetrator’s path of entry and exit  The investigator then proceeds with an initial walk through of the scene to gain an overview of the situation and develop a strategy for the systematic examination and documentation of the entire crime scene.  This is done before processing the crime scene for physical evidence

The Search The search for physical evidence at a crime scene must be thorough and systematic The search pattern selected will normally depend on the size and local of the scene and the number of collectors participating in the search Physical evidence can be anything from massive objects to microscopic traces

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 scrapings, in addition to more discernible items

Beyond the Crime Scene The search for physical evidence must extend beyond the crime scene to the autopsy room The medical examiner or coroner will examine the victim to establish a cause and manner of death Tissues and organs will be retained for pathological and toxicological examination

Beyond the Crime Scene The following are to be collected and sent to the forensic Laboratory  Victims clothing  Fingernail scrapings  Hairs  Blood (for DNA typing purposes)  Recovered bullets from the body  Hand swabs from shooting victims

Packaging Each different item collected at different locations must be placed in separate containers. Packaging evidence separately prevents damage through contact and prevents cross-contamination

Packaging Forceps and similar tools may have to be used to pick up small items Unbreakable plastic pill bottles with pressure lids are excellent containers for hairs, glass, fibers, and various other kinds of small or trace evidence Manila envelopes, screw-cap glass vials are adequate containers Do NOT use mailing envelopes (powders can leak out)

Packaging Small amounts of trace evidence can also be conveniently packaged in folded paper Two frequent finds at crime scenes warrant special attention  If bloodstained materials are stored in airtight containers, the accumulation of moisture may encourage the growth of mold which can destroy the value of blood  In these instances, wrapping paper, manila envelopes, or paper bags are recommended packaging materials

Packaging the Evidence Crease a clean paper and place the evidence in the x position (as shown above) Fold 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

Chain of Custody In order to present credible evidence in court, a chain of custody log is essential  A person bags the evidence, marks it for identification, seals it and signs it across the sealed edge.  It is signed over to a technician in a lab for analysis who opens it, but not on the sealed edge  After analysis the technician puts it back in the evidence bag and signs the evidence log

Analyze the Evidence The facts of the case are determined when the forensic lab processes all the collected evidence The lab then sends the results to the lead detective who aims to see how it all fits into the crime scenario

Analyze the Evidence The lab results can  Show how reliable are any witness accounts  Establish the identity of suspects or victims  Show the suspects to be innocent or link them with a scene or victim

Crime Scene Reconstruction Crime scene reconstruction  Forming a hypothesis of the sequence of events  From before the crime was committed  Through its commission

Staged Crime Scenes When the lab results do not match up with testimony of witnesses, it can mean the crime was staged; common examples include  Staging a fire ~ to cover bankruptcy  Staging a suicide ~ to cover a murder  Staging a burglary – to collect insurance money

Staged Crime Scenes To help determine whether a crime scene was staged, consider  Whether the type of wound found on the victim matches the weapon employed  Whether the wound could have been easily self-inflicted  The mood and actions of the victim before the event  The mood and actions of the suspect before the event.

Crime Scene Safety The increasing spread of AIDS and hep B has sensitized the law enforcement community to potential health hazards In reality, officers have an extremely small chance of contracting AIDS or hep at a crime scene

Legal Considerations at a Crime Scene Warrant-less searches ~ Illegal Circumstances under which the police can search without a warrant?  Existence of emergency circumstance  Need to prevent the immediate loss or destruction of evidence  In connection of a lawful arrest  Search made with the consent of the parties involved

Mincey v. Arizona  under the pretext of buying drugs, police forced entry into Rufus Mincey’s apartment and an undercover officer was killed  over a 4 day period police gathered evidence without a warrant  Mincey was convicted but appealed saying the evidence was collected without a warrant or his consent

Mincey v. Arizona Con’t The court upheld Mincey’s position stating that the police had time to obtain a warrant since Mincey was in custody

Michigan v. Tyler  a fire burned down Tyler and his partner’s business  police were prevented from immediately searching the scene due to smoke, darkness, etc.  the next morning evidence was collected and removed

Michigan v. Tyler Con’t  4, 7, and 25 days later more evidence was collected without a warrant and was used to convict Tyler and his partner of arson  The Supreme Court overturned the decision stating the evidence collected that morning was proper and did not need a warrant but the additional entries did require a warrant