Forensics Quiz #2
Crime Scene Investigators
Trained to recognize, document, photograph, and collect all forms of evidence at a crime scene
It is almost impossible for a crime to be committed without the perpetrator leaving behind some type of evidence (fingerprint, hair, human cells)
Crime Scene Investigations
Recognize, document, photograph, and collect evidence at the scene of the crime
Evidence must be reliable and valid or it will not be permissible in court
Evidence must be scientific, objective, and properly collected
CSI Team
made of legal and scientific professionals that work together to solve a crime
Police officers- first at the scene and secure the scene. Must be trained in basic forensic techniques, especially in smaller towns
District attorneys- will determine whether a search warrant is necessary
CSI’s- document the crime scene in detail and collect physical evidence
Medical Examiners (coroners)- determine the manner of death (natural, accidental, homicide, suicide or undetermined)
Detectives- interview witnesses, CSI’s, and specialists to obtain evidence that help to reconstruct the crime scene
Specialists- may include:
forensic pathologist (to identify remains)
botanists (can determine time of year or region of the world a crime took place),
entomologist (will estimate the post mortem interval, or time since death)
Called in only if neededPolice officers- first at the scene and secure the scene. Must be trained in basic forensic techniques, especially in smaller towns
District attorneys- will determine whether a search warrant is necessary
CSI’s- document the crime scene in detail and collect physical evidence
Medical Examiners (coroners)- determine the manner of death (natural, accidental, homicide, suicide or undetermined)
Detectives- interview witnesses, CSI’s, and specialists to obtain evidence that help to reconstruct the crime scene
Specialists- may include:
forensic pathologist (to identify remains)
botanists (can determine time of year or region of the world a crime took place),
entomologist (will estimate the post mortem interval, or time since death)
Called in only if needed
Locard’s Principle of Exchange (Dr. Edmond Locard)- whenever two people come into contact with each other, or with an object, a physical transfer occurs (hair, skin cells, clothing fibers, pollen, glass fragments, etc.)
Indicates that two objects, or people, were in contact with each other
The more intense, or longer the exchange, the more evidence will be transferred
Trace evidence- transferred materials between people or objects
Pet hair, hair on brushes, fingerprints, soil tracks, drop of blood, used facial tissue, broken glass fragments
Direct Evidence- first hand observations such as eye witness accounts or police dashboard video cameras (can include confessions)
Circumstantial Evidence- indirect evidence used to imply a fact, but does not prove it
May provide a link between a crime scene and the suspect
Finding the suspect’s gun at a crime scene links him/her to the scene but does not prove who used it
Can be physical or biological evidence
Physical- fingerprints, shoeprints, toe prints, tire impressions, tool marks, glass, soil, fibers, weapons, bullets, and shell casings
Biological- DNA in tissue, bodily fluids, hair, plants, pollen and natural fibers
Class v. Individual Evidence
Class Evidence- narrows the identity to a group of persons or things
Finding a certain blood type narrows the suspect list down to those who have that type, and eliminates those with other blood types
Individual evidence- narrows the search down to a single individual- only belongs to one person (fingerprint)
Step 1- Securing the Scene- responsibility of the first responder or law enforcement
Safety of individual is the first priority, followed by the preservation of evidence
Protect the area where the crime has occurred, restrict all unauthorized individuals
Prevents Locard’s Principle of Exchange
Step 2- Separating the Witnesses- keeping the witnesses separated prevents them from working together to create a story, or collusion
Witnesses are asked a series of questions:
When did the crime occur?
Who notified law enforcement?
Who is the victim?
Can the perpetrator be identified?
What did you see happen?
Where were you when you observed the crime scene?
Step 3- Scanning the Scene- by scanning the scene, a CSI can determine where photos should be taken
Primary Crime Scene- location of the crime
Robbery in front of a store
Secondary Crime Scene- movement to a new location for evidence
The home of the suspect that committed the robbery
A murder may have taken place at a certain location (primary crime scene) and the body was moved to another location (secondary crime scene)
Step 4- Seeing the Scene- using photos of the area, both up overall and up close photos
Using measuring rulers and reference points to compare photos
Triangulation- technique used to record evidence location from two fixed reference points
Uses photos from many locations and angles
Step 5- Sketching the Scene- CSI makes an accurate sketch of the scene and notes remains and any other evidence
North should be identified and distance scale should be provide
Unknown
All objects should me measured and all structures drawn as accurately as possible (doors, windows, trees, shrubs, etc.)
Specialized software can be used at a later time to make a detailed image of the scene for possible use in court
Step 6- Searching for Evidence- CSIs search the area in a systematic way to make sure the whole area is covered
Patterns of search include grid, linear, quadrant or zone, and spiral
Each technique ensures that the whole area is searched
All evidence should be photographed, sketched, labeled and documented
Special equipment such as thermal imaging, blacklights, and satellite images can help with the search
Step 7- Securing and Collecting Evidence- all evidence needs to be properly packaged, sealed and labeled
Liquids and arson remains are stored in airtight, unbreakable containers
Biological evidence is stored in breathable containers allowing it to dry out and reduce mold contamination
Evidence is then placed into a paper bindle (folded paper used to contain evidence) and then placed into a plastic container and sealed with tape and labeled
All evidence needs to be recorded in an evidence log that contains the case number, item inventory number, description of the evidence, name of suspect and name of victim, cate and time of recovery, signature of person recovering the evidence and signatures of any witnesses that are present during collection