Crime Lab Investigation
Sponsored Links
This presentation is the property of its rightful owner.
1 / 81

Crime Lab Investigation PowerPoint PPT Presentation


  • 147 Views
  • Uploaded on
  • Presentation posted in: General

Crime Lab Investigation. Forensic Detectives. Hollywood vs. the Real Forensic Detectives. #1 Task. Determine if there is physical evidence that connects the suspect to the crime. Is there evidence that places the suspect at the crime scene? If so...

Download Presentation

Crime Lab Investigation

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Crime Lab Investigation


Forensic Detectives

Hollywood vs. the Real Forensic Detectives


#1 Task

  • Determine if there is physical evidence that connects the suspect to the crime.

  • Is there evidence that places the suspect at the crime scene? If so...

  • Is there evidence that shows the suspect actually committed a crime at the crime scene?


Approach

  • Take advantage of the fact that there is always some exchange of physical evidence between criminal and the crime scene

  • Either criminal leaves something at the crime scene that can be connected to him/her...

  • Or criminal picks up something at the crime scene that connects him/her to the scene.


Evidence Collection

  • Forensic scientists (also called criminalists) do not normally go into the field to collect evidence except for high profile cases.

  • They normally train detectives and police officers to perform the task of evidence collection.


Evidence Examination

  • The “physical match” is the strongest form of evidence.

  • It is strong because of the certainty of connecting suspect to crime scene.

  • In the court it is more convincing because of the obvious visible match.


Evidence Examination

  • If a physical match is not possible, do comparisons.

  • Use equipment that makes comparisons easier.


Click on image to see split screen of two casings.


Evidence Examination

  • When identification is needed, screen first, then identify.


Heroin

Amphetamine

Marquis Reagent


Duquenois-Levine Reagent


HIGH PRESSURE

LIQUID CHROMATOGRAPHY

CHROMATOGRAPHY

WRITE

COLOR


Thin Layer Chromatography (TLC)


GAS CHROMATOGRAPHY


GAS CHROMATOGRAPH


Blood Samples from DUI Cases


Gas Chromatograph - Mass Spectrometer

GC-Mass Spec

Separates (purifies) the different compounds from a mixture. Can give a positive identification or at least a strong indication of a substance’s identity.

Measures the Mass (formula weight/molecular weight) of the substance, which completes the identification.


Automation

For

CourtroomCredibility

Faster testing

More reliable testing

  • Run a known standard

  • Run a blank

  • Run the unknown

For comparison purposes


Documentation

is Critical

Computer skills are needed

Keyboarding skills are needed


PCR Thermal Cycler

  • The Polymerase Chain Reaction (PCR) is a technique where a sequence DNA can be amplified (duplicated) a billion fold in just hours.

  • Minute samples of DNA isolated from blood at a crime scene can be used to determine if an individual was actually at the location of the crime.


Visualization Techniques


Forensic Detectives

Hollywood vs. the Real Forensic Detectives


Pictures and animations byKen Costello

Pictures and animations byKen Costello


  • Login