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

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

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

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

SECURE THE SCENE

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?

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)

CSI Unit Sketcher Photographer Searcher (evidence collector) Documenter

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

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

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

**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.

Photographing Evidence – Mark evidence with tents

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

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

Overall Shots – Inside the Scene

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

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

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.

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

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.

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.