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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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.



Evidence examination2
Evidence Examination

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


Heroin

Amphetamine

Marquis Reagent



HIGH PRESSURE

LIQUID CHROMATOGRAPHY

CHROMATOGRAPHY

WRITE

COLOR






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
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.



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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