#1 Task Determine if there is physical evidence that connects the suspect to the crime.Determine if...

#1 Task

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

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

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

Approach

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

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

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

Evidence Collection

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

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

WRITECOLOR

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.

1) Run a known standard

2) Run a blank

3) Run the unknown

ForCourtroomCredibility

For comparison purposes

Documentationis Critical

Computer skills are neededKeyboarding 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

Pictures and animations byKen Costello

Pictures and animations byKen Costello

Pictures and animations byKen Costello

Pictures and animations byKen Costello