Crime Lab Investigation
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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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Crime lab investigation

Crime Lab Investigation


Crime lab investigation

Forensic Detectives

Hollywood vs. the Real Forensic Detectives


1 task

#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

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

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

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 examination1

Evidence Examination

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

  • Use equipment that makes comparisons easier.


Crime lab investigation

Click on image to see split screen of two casings.


Evidence examination2

Evidence Examination

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


Crime lab investigation

Heroin

Amphetamine

Marquis Reagent


Crime lab investigation

Duquenois-Levine Reagent


Crime lab investigation

HIGH PRESSURE

LIQUID CHROMATOGRAPHY

CHROMATOGRAPHY

WRITE

COLOR


Crime lab investigation

Thin Layer Chromatography (TLC)


Crime lab investigation

GAS CHROMATOGRAPHY


Crime lab investigation

GAS CHROMATOGRAPH


Crime lab investigation

Blood Samples from DUI Cases


Crime lab investigation

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.


Crime lab investigation

Automation

For

CourtroomCredibility

Faster testing

More reliable testing

  • Run a known standard

  • Run a blank

  • Run the unknown

For comparison purposes


Crime lab investigation

Documentation

is Critical

Computer skills are needed

Keyboarding skills are needed


Pcr thermal cycler

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

Visualization Techniques


Crime lab investigation

Forensic Detectives

Hollywood vs. the Real Forensic Detectives


Pictures and animations by ken costello

Pictures and animations byKen Costello

Pictures and animations byKen Costello


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