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

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

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

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

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

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

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

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

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

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