How Crime Scene Investigation Works

CSI Basics The goal of any investigation is to convict the perpetrator of the crime. Need to gather physical evidence without disturbing trace evidence Need to preserve evidence in current form Need to consider what the lab will need to do with the evidence Need to consider the legal issues of making evidence admissible in court.

Who is there? Police CSI unit District attorney Medical examiner

Police on the scene Police are typically first to arrive Arrest the perpetrator if still on site Call for an ambulance if needed Secure the scene.

CSI Team Documents the scene and collects evidence

District Attorney If the investigators need a search warrant Obtains search warrants from judge

Medical Examiner In the case of a homicide Determine preliminary cause of death

Steps of a CSI investigation Call is made from the police or detectives on the scene to the CSI team to come investigate Police must be sure the scene has been secured No random people wandering and disturbing evidence

Initial walk-through CSI gets an overall feel for the crime scene Find out if anything has been moved Makes general initial theories Makes a note of potential evidence At this point - TOUCHES NOTHING!

Documents the Scene Taking photographs and making sketches during a second walk-through. Walk-through is often done with videotape CSI still touches NOTHING

Collect all potential evidence Tag, log, and package evidence to stay in tact until it reaches the lab CSI may or may not do any analysis of evidence depending upon their individual field.

Crime Lab Processes all evidence Lab results will go to the lead detective

Video clip http://science.howstuffworks.com/csi.htm

At the crime scene Scene recognition

Extent of crime scene Define the boundaries of the crime scene Example: a homicide Victim, the house, area around house, cars in the driveway, blood trails, could become quite large

Securing the crime scene Consider other areas that might be part of the crime scene CSI gets one chance to gather all possible evidence Evidence becomes corrupted

Core area Most obvious part of the crime scene where the most evidence is concentrated Usually secured by police CSI usually extends the area after walk-through Also contains a safe area to maintain the core area to decrease the potential for error

Search warrant CSI will obtain a search warrant Ensures the evidence will be admissible in court

Walk-through CSI takes immediate note of details that will change over time Weather Time Smells Sounds Smoke Also checks for potential hazards Gas leaks Fire Dogs Other suspects

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