1. Crime Scene Investigation
The 7 S’s of Crime Scene
Investigation

2. 1.Securing the Scene First responding officer – it is his/her duty to
secure the scene by limiting access to the scene and
preserve scene with minimal contamination
1st priority – secure safety of all individuals in the scene
by limiting access to it
2nd priority –preservation of evidence
Locard’s exchange principle –
contact between individuals and
locations leads to an exchange of
trace evidence

3. 1.Securing the Scene First officer on scene responsibilities
(check list handout):
Secure safety of individuals at the scene
Approach scene cautiously (look, listen, smell)
Obtain medical attention for anyone injured
Call in backup help, including medical and CSU personnel
Separate witnesses
Perform initial walk-through (scan the scene)
Search scene briefly to notify lab of equipment needed
Collect information, including address/location of the scene, time date, type of call, names and addresses of all parties involved and present
Securing integrity of the scene by establishing boundaries of the scene and setting tape around parameter
Protect crime scene by remaining alert and attentive
Document the entry and exit of all authorized by keeping a security log
Provide brief update to the next-of-command officer to arrive on scene

4. 2.Separating the Witnesses
3rd priority – witnesses must not be allowed
to talk to each other to avoid
collusion (creation of story by
witnesses talking to each other)
Questions to ask:
When did crime occur?
Who called in the crime?
Who is the victim?
Can the perpetrator be identified?
What did you see happen?
Where were you when you observed the crime scene?

5. 3.Scanning the Scene Scan the scene to
a. determine where to take photos
b. determine primary crime scene
c. determine secondary crime scene
( if this applies to the case)

6. 4.Seeing the Scene Examiner needs: Photos of overall area
Close-up photos with and without measuring ruler
Photos of triangulation of stationary objects
Photos taken from different angles and distances
Several close-up photos of any evidence and body(/ies)

7. 5.Sketching the Scene A rough sketch of the scene is made
noting – position of body (if any)
any other evidence
Sketch should include:
Objects measured from 2 immovable landmarks
North should be labeled
Scale of distance should be provided
Objects in the vicinity of the scene should be included
Indoors: doors, windows, furniture, etc
Outdoors: trees, vehicles, hedges, etc

8. 5.Sketching the Scene Final Sketch – done later more accurate copy
used in court proceeding
computer programs can be
used
Should include:
North
Scale
Case #
Date
Location
Name of officer/investigator

9. 6.Searching for Evidence
Searching for evidence should be systematic
Types of searches:
Spiral
Grid
Linear
Quadrant or zone

10. 6.Searching for Evidence
The type of search depends on:
Area of the crime scene
number of investigators present
The location of evidence should be:
Marked
Photographed
Sketched

11. 7.Scene Evidence Collection
Evidence needs to be – properly packaged
sealed
labeled
Liquids and arson – stored in airtight
unbreakable containers
Biological evidence – stored in breathable
containers for evidence to
dry out to reduce mold growth

12. 7.Scene Evidence Collection
Biological evidence – a. Needs to dry out in
breathable container
b. Is stored in paper
bindle (druggist’s fold)
c. Placed in plastic or
paper container
d. Is later sealed w/tape
e. Collector signs his/her
name across the tape

13. 7.Scene Evidence Collection
An evidence log and chain of custody document must be attached to the evidence container
Evidence log should contain:
Case #
Item inventory #
Description of evidence
Name of suspect
Name of victim
Date and time of recovery
Signature of person recovering evidence
Signature of any witness present during collection

14. 7.Scene Evidence Collection
Packaging Evidence:
Choose appropriate-size sheet of clean paper for bindle
Crease paper into portions/partition size depends on evidence size
Place evidence in a central location on paper
Evidence

15. 7.Scene Evidence Collection
Fold paper left and right sides in
Fold in top and bottom
Insert the top flap into the bottom flap
Tape-close
Place bindle inside a plastic or paper bag
Fold bag closed
Place a seal over the folded edge of evidence bag
Have collector write his/her name across folded edge

16. 7.Scene Evidence Collection
Wet evidence should never be packaged in plastic container
DNA will degenerate
Evidence may become moldy, thus useless
Control samples must also be obtained from victim for exclusion

17. Chain of Custody Essential in securing the evidence:
Individual who finds evidence marks it for id and bags it
Final container for evidence is a collection bag which is labeled and then sealed
Collector’s signature is written across sealed edge
Container is given to next person responsible for its care
That person takes it to the lab and signs it over to the technician
Technician opens package for examination
After examination, technician repackages evidence within its original packaging
Technician reseals evidence in a new packaging
Technician seals, signs name across label seal
Technician signs the chain of custody log attached to the packaging