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Crime Lab Investigation

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...

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Crime Lab Investigation

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  1. Crime Lab Investigation

  2. Forensic Detectives Hollywood vs. the Real Forensic Detectives

  3. #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?

  4. 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.

  5. 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.

  6. 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.

  7. Evidence Examination • If a physical match is not possible, do comparisons. • Use equipment that makes comparisons easier.

  8. Click on image to see split screen of two casings.

  9. Evidence Examination • When identification is needed, screen first, then identify.

  10. Heroin Amphetamine Marquis Reagent

  11. Duquenois-Levine Reagent

  12. HIGH PRESSURE LIQUID CHROMATOGRAPHY CHROMATOGRAPHY WRITE COLOR

  13. Thin Layer Chromatography (TLC)

  14. GAS CHROMATOGRAPHY

  15. GAS CHROMATOGRAPH

  16. Blood Samples from DUI Cases

  17. 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.

  18. Automation For CourtroomCredibility Faster testing More reliable testing • Run a known standard • Run a blank • Run the unknown For comparison purposes

  19. Documentation is Critical Computer skills are needed Keyboarding skills are needed

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