Forensic Science

What happens at the Crime scene?

• Sequence of events
• Modus operandi
• Motive

Step 1:  Protect and secure

• Protect the lives of people
• Protect the scene 
• Interview witnesses

Step 2:  Observe and Document

• Search for possible evidence
• Points of entry and exit
• Note taking

Step 2:  Observe and Document: Notes

• Date and time
• Location description
• Weather and environmental conditions
• Evidence location
• Name of all people (witnesses, victims, etc)

Step 3:  Photograph/Video

• Scene must be photographed before any changes

Step 3:  Photograph/video

• Provide judge and jury with details
• clarification of the scene
• close-up of evidence with ruler for scale
• "eyes" of the witness

Step 4:  Sketch the scene

• Perspective to photographs
• Investigators can select important items
• Gives measurements, relative placement of objects

Step 4:  Sketch should include

• Date and time
• Names of all people
• Scale
• Reference points
• Distance measurements

ROugh Sketch

• Initial pencil drawing at the crime scene
• "N" must be at the top of the paper
• All distances included
• Select 2 "fixed points"
• All objects included with legend

Final Sketch

• Use rough sketch
• Convert drawing use a conversion 
• For example, 10 ft = 1 cm

Step 5:  Searching the Scene

• Anything that should not be there
• Trace evidence
• Special lighting, such as UV
• May use a grid system

Step 6:  Packaging the evidence

• Each item in a separate container with label
• Follow Chain of Custody

Step 6:  Packaging: Special considerations

• Wet items must be dried
• Containers should be tightly sealed
• Biological items in freezer
• Items with trace evidence carefully packaged
• Firearms should be in wooden container

Step 6: Packaging: Special considerations

• Items from suspected arson in airtight container
• Special vacuum can be used
• Controls must be collected

Chain of custody

• Written record
• People who had contact with "evidence"

chain of custody

• Item number and description
• Date and time
• Transfer signatures
• Reasons for transfer

THe Crime Scene