1. Crime Scene Investigation Methods
Ch. 2 The Crime Scene
Crime Scene Investigation Methods

2. Investigating the Crime Scene
There are several steps that must be taken when investigating a crime.
Some of the steps must be completed in order, while others just must be completed

3. Step 1: Secure & Isolate Crime Scene
Preserves evidence
Prevents damage to evidence as well as removal of evidence
Keeps others from contaminating scene with new evidence
Authorized personnel only
Scene is determined by initial witness statements and visual scan of area

4. Step 2: Record the Scene
Scene must be documented both as a whole and individual pieces of evidence
Measurements are taken to determine the distance between objects, size of the area, etc
Evidence is marked as it is photographed
Photography/Videography
Sketch of scene – rough & final

5. Step 3: Search for Evidence
Depending on type of crime, you might search for different types of evidence
Murder weapon, tool marks, entry, blood, etc
4 main methods of searching:
Spiral
Grid
Strip
Quadrant
Must seek evidence beyond crime scene:
Suspect house/vehicle, dumpster nearby, water area, underground, in ashes, hospital/morgue

6. Step 4: Collect & Package Physical Evidence
Process scene in a way that prevents any change from taking place
Prevent contamination, evaporation, scratching/bending, breakage, loss, etc
Examples: garments of victim/suspect, swabs/scrapings from walls, bullets, etc
Individually packaged in appropriate container
Labeled with location, time, date, who collected it

7. Chain of Custody
Initial collector labels all evidence with time, date, location, and initials
Whoever opens the evidence next records that in the evidence log and on the evidence bag
Transfers are also recorded
DNA evidence mailed to crime lab
Officer given evidence to bring back to lab

8. Step 5: Obtain Reference Samples
Reference samples come from victim, other people at scene (possibly residents/employees), possible suspects in custody, etc
DNA (buccal swab) and fingerprints
Other reference samples may be known substances or objects to be used to compare with evidence found
Common “white powders”, tool marks, wound patterns, bugs, substrate materials

9. Step 6: Submit Evidence to Lab
Peronally delivered or mailed
Evidence submission form is sent with the evidence
Some results can take up to several weeks

10. Crime Scene Precautions
Protective clothing should be worn
Blood/bodily fluids may contain diseases
Toxic fumes may be present
Biohazard containers used to store evidence/waste that has body parts/fluids
Gloves – to prevent fingerprints from contaminating scene
No food or beverages
Uncontaminated note taking