The Investigation - PowerPoint Presentation

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The Investigation

Crime Scene: The place or site where the crime took place.Slide2
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Arriving at the Crime Scene

When officers arrive at the crime scene, they have three tasks to perform:1. Assist injured people and call an ambulance, if necessarySlide4

2.

Eliminate any hazards or threats that may still exist.Slide5

3. Continue to search and protect the crime scene, even if the perpetrators have left.Slide6

Protecting and Preserving the Crime Scene

To protect the crime scene, officers establish two boundaries: 1. the center (where the crime was actually committed)

2. the

perimeter

(the

surrounding area where a perpetrator may have been or may have left

evidence)

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Preservation of Crime Scenes

Crime scenes are preserved for three reasons:To allow for a thorough search of the crime sceneTo find and collect physical evidence

To ensure that the physical evidence seized is admissible in court.Slide9

Contamination

Contamination is the loss, destruction, or alteration of physical evidence. (Remember the blanket in the Simpson case.)Contamination of evidence may lead to: - evidence being held inadmissible in court

- police being led in the wrong direction

- doubt in the mind of jurors/judge

Crime scene and evidenceSlide10

Identifying and Collecting Physical Evidence

How do you prove that the accused was there???One important way is by collecting and presenting physical evidence.Physical evidence is any object, impression, or body element that can be used to prove or disprove facts relating to an offence.Slide11

Forensic Evidence

Forensic science is the application of biochemical and other scientific techniques to criminal investigation. (CSI) Forensic scienceSlide12

Impression Evidence

Impressions:- Patterns or marks found on different objects caused by different objects such as fingers (fingerprints), shoes, tires, tools.Slide13

Collecting and Matching Impression Evidence:

Record the impression by a photograph and then a scan or mold. Match the impression with the object that made itSlide14

Impressions have 2 characteristics:

Class characteristics - the general attributes (characteristics) of an object.

(Ex. With tires, class characteristics might include things like: 14 inch, radial, tires manufactured by B. F. Goodrich, supplied with all 2003 and 2004 Hyundai Elantras

Individual characteristics

-the features specific and unique to the particular object.

(Ex. Still using our tire example, the individual characteristics would be the tread wear, evidence of a repaired flat, the type of soil found in the treads.)Slide15

Fingerprints

a patterned mark left on an object by a fingertip. can also take prints of feet, hands and toes. Fingerprints “never” change and are unique to the individual.Even identical twins have different fingerprints. Slide16
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Two types of fingerprints

Visible - Can see it with the naked eye - Usually coated in dirt, grease or blood. - Can usually be photographed right away.

Fingerprints

Latent

-

Cannot be seen with the naked eye

- Made by perspiration and body oils

- Has to be “developed”

before it is photographed. (3 ways to do this)Slide18

Shoe prints and tire tracks can be matched to put the suspect at the scene.

tire tracks Slide19

Remember class characteristics and individual characteristics…. What might the class characteristics of a sneaker print be? What might some of the individual characteristics be?Slide20

Body elements and DNA

DNA Evidence Investigation and DNASlide21
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DNA Fingerprinting Activity

Fingerprinting Activity (Nova and the Sheppard case) Questions Appendix ASlide23

The chain of custody is the witnessed, written record of all of the people who had control of the item in evidence.

Chain of custody