What is forensics?
Forensics comes from the latin work, forensis, meaning of the forum (a place where people would go to mediate problems like a modern-day court).
What is forensic science?
The application of science to solving crimes, answering the who, what, where, when, why, and how.
What is a crime scene?
A crime scene is a location where the crime took place or something to do with the crime to place.
There are two kinds: Primary and Secondary.
Primary crime scene
The original location the crime actually took place, there can only be one.
Secondary crime scene
A location other than the primary scene where evidence may be found, there can be more than one.
Ex. Maybe the suspect planned it in their basement, maybe they transported a body in their car and dumped it in a ditch, etc.
Who is involved at a crime scene?
Police officers: usually the first on the scene, they secure the scene and call for warrants.
Crime Scene Investigators: document the scene, collect evidence, conduct field tests.
Coroner: Determine the manner of death.
Detectives: Interview witnesses, nadle legal aspects
Scientific specialists: May be consulted if an expert is needed in a specific way (blood splatter analyst, etc)
How are crime scenes investigated?
using the seven s’s of a crime scene.
What are the seven s’s in order
- Secure the scene
- separate the witnesses
- scan the scene
- see the scene
- sketch the scene
- search for evidence
- secure and collect evidence
Secure the scene
Responsibility of the first responding police officer(s).
- They secure the scene using police tape and making sure that everyone is safe. They may even call medical help.
- Isolating the area is done to preserve the evidence
- The officer completes a security log of anyone who visits the scene
Separate the witnesses
Police officer or detective will talk to witnesses
- Witnesses should not talk to each other
- This is because we do not want them collaborating to create a false story.
Scan the scene
Done by lead CSI
- walk-through is done to determine type of scene (crime, primary, secondary) and formulate a plan as to how they want to go about the rest of the investigation.
See the scene
Done through the eyes of a camera lense
- Photography unit takes pictures of all items identified during initial scan
- Photos are taken of the overall scene and close up
Sketch the scene
A sketch is created of the scene so that CSI can recreate it in their lab identical to the real thing.
Sketch must include:
- All objects in the room
- location of the evidence (x)
- Directional north
- date, time, location, and case number
- distance scale
Search for evidence
A thorough search is conducted to identify any evidence that may have been overlooked in the previous steps.
- Search pattern is chosen by the lead investigator
- Grid, Linear, Quadrant, and Spiral
Secure and collect evidence
All evidence identified must be collected using specific steps and procedures.
- Must be documented before collection
- Liquids and arson remains: airtight, unbreakable containers
- Biological evidence: if moist, put in a container until dry.
- Once dry: place in paper bindle for trace or plastic or paper container.
- Other evidence: paper, plastic, or envelope.
Locard’s exchange principal
When two people meet each other or with an object, a cross-transfer of material occurs. The intensity, duration, and nature of the objects and contact determine the extent of the transfer.
What is evidence
Any object or material left at a crime scene that supports investigators in their case and leads them to their answers.
Types of evidence
Direct
Indirect
Physical
Biological
Class
Individual
Direct evidence
Any evidence that directly supports what was thought to be an alleged fact of a case.
-Proof or very very close to
-eyewitness, dash cam, security footage, confession suicide note…
- Ex. you saw the snow fall last night
Indirect evidence
Evidence that is used to imply a fact, but does not prove it.
- may provide a link between a suspect and the crime scene
-Ex. You went to be while the grass was still showing, and when you woke up, it was covered in snow. You know it must have snowed but you can’t directly prove it.
Physical evidence
a type of indirect evidence that does not contain DNA.
- can be made by something alive but it itself does not contain DNA
-Impressions, fingerprints, shoe prints, synthetic shirts, weapons, etc
Biological evidence
a type of indirect evidence that contains DNA
- skin cells, bodily fluid, animal hair, human hair, nails plants, natural fibres, etc.
Class evidence
evidence that narrows down the suspect to a group of people.
-can be either physical or biological
-blood type, tire marks, shoe size, hair colour
- With proper investigation, can be turned into individual
Individual evidence
a type of evidence that narrows the suspect down to one person.
- can be physical or biological
-fingerprint, DNA, etc. - anything unique to one person.
