1. Roles of the Forensic Scientist
At the crime scene
Roles of the Forensic Scientist

2. A Recent history
It is important to look at crime scenes as pieces of recent history that need to be investigated in order to put together a full story of what happened.
Specific methods:
Plan for systematically searching the site
Consider safety of the scene searchers
Highly qualified personnel only
Contamination of scene minimized
Gather and analyze information QUICKLY
Document the crime scene thoroughly
Develop and maintain chain of custody

3. Discovering the crime A witness reports the crime
A victim reports the crime
A police officer discovers the crime in progress (sting operation)

4. Seven s’s of csi Secure the scene Separate the witnesses
Scan the scene
See the scene (photography)
Sketch the scene
Search for evidence
Secure and collect evidence

5. SECURE THE SCENE

6. First responder Securing and scanning the scene…
Is the perpetrator still there? (Hot vs. Cold Search)
Are there any injured people?
Secure the scene to minimize contamination
DO NOT walk through and search for evidence
Are there any obvious safety hazards?

7. CSI unit Primary Crime Scene – where the original crime took place
Secondary Crime Scene – where evidence was carried to by a suspect (where body was found)

8. CSI Unit Sketcher Photographer Searcher (evidence collector)
Documenter

9. Search for evidence Grid, strip or lane, spiral search pattern
Use flashlight to find hair and fibers
Use forceps, vacuum cleaner to collect evidence
Grid
Strip or Lane
Spiral

10. Collecting evidence
“You cannot make chicken salad out of chicken feathers.”
Chain of Custody – A log maintained for each piece of evidence that documents who handled it, how, and when
Begins when the evidence is discovered
Most important part of evidence collection/analysis
Recognition, Collection, Packaging and Preservation

11. Evidence RECOGNITION
Forensic investigators must determine what is evidence by knowing what should be at a scene and what should not.
Investigators have extensive knowledge based on experience, but if there is ever any question if something is evidence, it should be collected just in case.
Homicides – weapon, blood, fibers, hairs, fingerprints
Sexual Assault – hairs, fibers, body fluids

12. **Once a scene is handed back over to owners, they CANNOT go back and collect more evidence.
After evidence is located, it’s location must be thoroughly documented before collection.

13. Photographing Evidence –
Mark evidence with tents

14. Photographing Evidence
Show the scene exactly as it was when you found it – do not move anything or try to reconstruct the scene.
Take pictures outside of the scene – aerial shots, photograph all doors/exits
Take pictures inside the scene – start at the door, then photograph the room from all possible angles

15. Three types of shots: Overall – shots from the entrance and each wall
Mid-Range – picture of evidence as it is related to it’s surroundings
Close-up – bring out details of the item
One shot with measuring tool
One shot without

16. Overall Shots – Inside the Scene

17. Evidence: Knife (possible weapon)
Midrange Photo
Close-Up (with ruler)

18. Sketching the Scene Make an accurate rough sketch
Denote N (direction) and relative scale for size
Include relevant objects – body, door, furniture, immovable landmarks

19. Evidence collection
Collect as much evidence as possible – consider that some might be lost in analysis
Collect knowns or comparison samples
Probative value – significance of a piece of evidence. This can be increased if evidence can be linked to a known material or object
Ex. Fingerprints on a weapon have no probative value unless they can be linked to the known fingerprints of a suspect.

20. Packaging and preserving evidence
Chain of Custody – legal record of all people in possession of a piece of evidence. Helps produce evidence that is authentic.
IF THE CHAIN OF CUSTODY IS COMPROMISED, EVIDENCE WILL NOT BE ADMISSIBLE IN COURT!!
Packaged in tamper-evident packaging, meaning that it is easy to tell if someone accessed the evidence who was not supposed to.
Tamper-evidence bags and boxes
Evidence tape – shreds easily (cannot be reapplied), and glue leaves behind a clear residue if removed

21. Packaging and preserving evidence
Packaging is determined by the type of evidence – needs to be preserved for as long as possible.
Living plants (i.e. marijuana) – “breathable” container, like a paper bag
Wet blood or Body Fluids – allowed to dry, then packaged OR packaged in a breathable container; blood can also be packaged in a glass tube containing a preservative.

22. Wet paint – allowed to dry, or packaged in breathable container
Small amounts of powder – bindle, then envelope or baggie
Fire residues – Airtight container – unused paint can (if put in breathable container, the accelerant will evaporate)
Trace evidence (hair, fiber, paint chips, glass) – an envelope or plastic baggie that is sealed on all sides.
Sometimes, placed in a bindle, then into an envelope.