Crime Scene Investigation Flashcards
What is forensic science?
The application of scientific techniques to legal processes
What is a crime scene?
- location/surrounding area where a crime has occurred
- focus point of investigation and primary source of information for investigation
What are the definers of a crime scene?
- physical location (indoors, outdoors)
- primary/secondary location (primary: where the crime occurred, secondary: evidence found that links to primary)
- area size: macroscopic vs microscopic
- crime committed
What is Locards exchange principle?
When two objects come in contact with one another, an exchange of matter takes place
What factors affect the transfer of matter?
- pressure involved
- number of contacts
- ease of transfer (blood is easily transferred)
- form of evidence exchanged
- are of item involved in contact
What is evidence?
Information given in legal preceedings to support fact or proposition
What does evidence depend on?
Transfer and persistence
What is the essential information generated from a crime scene?
- establish the identity of a victim or suspect
- establish links between the scene and people/objects
- provide leads of further enquiry
- focus investigation
- corroborate other events
= leads to a reconstruction of events
What are the 3 types of evidence?
- Physical
- Trace
- Testimonial
What is physical evidence?
Any material or items found in the crime scene of on the victim
What is trace evidence?
Microscopic physical evidence that is found in small but measurable amounts
What is testimonial evidence?
Written or verbal statements given to police, common evidence in rape or assault trials
What are the 2 classes of evidence?
Direct
Circumstantial
What is direct evidence?
First hand observations, includes eyewitness accounts, cameras and confessions
What is circumstantial evidence?
Indirect evidence, may be used to imply or support and may link a suspect to a crime scene
What are the branches of circumstantial evidence?
Physical, biological
What are the investigation roles in Australia?
- Uniformed officer
- Detective
- Scene of Crime officer
- Forensic scientist
What are the investigative roles in the US?
- Police officer
- Detective
- Crime Scene Investigator
- Medical examiner
- Specialist
What does a uniformed officer do?
Usually the first to the scene, secures crime scene
What does a detective do?
Driving investigator and first called to scene by the uniformed officer
What does the scene of crime officer do?
Responsible for evidence collection, documentation, secure transportation of evidence to the laboratory
What does the forensic scientist do?
Receives evidence, undertakes scientific evidence, provides expert testimony in court, rare that they attend the crime scene
What does the chain of custody do?
Details the movement of the evidence from the time it was collected to its appearance in court - any unknown times in the time period could indicate tampering
What are the 5 steps of processing a crime scene?
- Securing the crime scene
- Crime scene survey
- Crime scene documentation
- Searching the crime scene
- Collection of physical evidence
What are the 3 scene cordons?
- Hot zone
- Warm zone
- Cools zone
What is the hot zone?
Encompasses the primary location of the crime, scene processing occurs here
What is the warm zone?
Approx 100m around the hot zone
What is the cool zone?
Area where media and pedestrians are permitted
What is the role of the first officer at the crime scene?
- initial actions determine the success of the investigations
- secures the scene against further disturbances since disturbance to the scene can not be reversed
- looks at: safety, detains individuals involved, identifies areas to secure, and cordon
What does securing the crime scene involve?
- large area
- records status
- restrict public
- secure area
What happens during a crime scene walkthrough?
- initial reconstruction
- note evidence status: collection of some evidence must occur sooner than other pieces
- note points of entry/exit - single point is determined
- assess call out needs
What are the different types of crime scene search patterns?
- Spiral
- Strip
- Grid
- Zone
What does collection of physical evidence involve?
- document process
- collect
- maintain security of evidence
- establish chain of custody
- avoid contamination/cross contamination
- obtain reference samples
- obtain elimination samples if needed
What should be documented at a crime scene?
- notification of personnel called to scene
- arrival/departure of personnel
- scene description (evidence, environment)
- victim description
What are the steps of the chain of custody?
- Scene of crime officer
- Transporting officer
- forensic experts analysis
- Secure storage (temperature and humidity controlled)
- Return to long term police storage
How does a crime scene reconstruction occur?
- evidence leads to hypotheses
- hypotheses are tested
- disproven hypotheses are thrown out, leaving a reconstruction theory
- evidence = court case
- no one piece of evidence a,one is enough to convict a suspect
What are 6 common causes of evidence contamination?
- Inappropriate collection methods
- Deliberate tampering
- Human error due to fatigue
- Not using gloves when handling evidence
- Packaging items of evidence together
- Not using single use equipment
What are two common areas during cross examination that a lawyer will attack regarding physical evidence?
Contamination and continuity
