1. Practical Crime Scene Processing
and Investigation
Greg Dagnan
Chapter 5 - Assessing the Scene

2. Learning Objectives
Identify the purpose of assessment.
Describe the function of barriers in maintaining
scene integrity and contamination control.
Identify and explain three factors when managing
scene access.
Identify the two approaches to team formation.

3. Learning Objectives .. continued
Identify and explain the five basic search patterns
used in crime scene examination.
Identify basic personal protective measures for
crime scene team members.
Explain the relationship of the media and police as
it pertains to crime scenes.

4. Crime Scene Processing Activities
The six crime scene activities and their basic
order are:
– Assessing
– Observing
– Documenting
– Searching
– Collecting
– Analyzing

5. Assessing
Assessment of the scene assists the investigator in
making a decision on what to do, when to do it,
and what resources may be required.
Assessment must be accomplished before taking
any action, but assessment is an on-going activity
as well.
The investigator is constantly assessing the scene
throughout processing.

6. Five Issues of Assessment
Assessment involves five basic issues, these are:
– Scope and complexity of the scene.
– Scene integrity and contamination control.
– Team approach and composition.
– Search methods to be used.
– Personal protective measures.
Assessment by the crime scene team always
involves a debriefing of the initial responders.

7. Debriefing of Initial Responders
Debriefing of the initial responders seeks to
answer the following questions:
– What is the scope and nature of the scene?
– What actions or alterations have been taken or noted by
first responders (including EMS)?
– What is the status of involved parties?
– What level of security has been established and what
further security actions are required?
Their observations may not always be accurate,
but they give the team a point to start from.

8. Scene Scope
Investigators should re-access the scene boundary
after debriefing.
They use the same criteria as the initial officer:
– Primary focal points.
– Avenues of entry or exit.
– Secondary scenes.
Based on experience they may recognize minor
nuances that require expanding the perimeter.

9. Contamination Control
Once the crime scene team is confident of the
scene scope, the team should act to further isolate
the crime scene.
Initial perimeters are often a single barrier,
leaving little if any buffer between the crime scene
and the on-lookers.

10. A Single Barrier Perimeter
Initial Scene Perimeter A single barrier is
fine for initial
purposes.
It does not provide
a sufficient buffer
for long term scene
Area entailing the actual crime scene.
effort.
Area outside controlled perimeter where
on-lookers and media may gather.

11. Multi-level Containment
Multi-level containment involves two barriers
which creates three areas of access:
– Inner Scene: This is the actual crime scene, where only
authorized investigators and crime scene technicians
operate.
– Working Area: This is an area surrounding the inner
scene, where other support police may enter, equipment
is staged and evidence is brought to.
– Outer Area: This is everything on the outside of the
second barrier, where on-lookers, media and others
may gather.

12. Multi-level Containment
Outer Scene Perimeter
Two perimeters
Inner Scene Perimeter provide for three
areas of access.
This keeps support
police out of the
Area entailing the actual
crime scene. actual scene and
Working area, evidence holding area and staging point
others at a safe
for equipment, it also provides a physical buffer between
the actual scene and unauthorized individuals.
distance.
Area outside the controlled perimeters.

13. Managing Access to the Scene
Once the perimeter is established, a decision must
be made on how the team will manage access to
the scene.
This involves identifying actual access points for
the team and establishing entry control points.
Determining how to access the scene isn’t always
difficult, but it isn’t always simple either.

14. Access Points to the Scene
Determining how to access the scene is a function
of three factors:
– What avenues of approach are available?
– Will these points expose operations to media scrutiny?
– What avenues of approach or exit did the offender use?
With these three factors in mind the crime scene
team decides what points they will use to access
the scene for processing purposes.

15. Access Points Issues
What avenues of approach are available?
– There may only be one point of access.
– Look for others.
Will these points expose operations to media
scrutiny?
– Is there a way to shield the access point from the media
and their prying eyes?
What avenue of entry or exit did the offender use?
– These are areas rich in evidence, so the team can’t
simply tromp through them.

16. Entry Control Logs
The scene often requires multi-level containment,
with several perimeters.
Entry control logs can certainly be used at any
perimeter, but they become a hindrance to
operations.
The inner perimeter (the true crime scene)
requires an entry control log.

17. Crime Scene Entry Control Log
Time In Name/Unit Reason at Scene Time Out
1750 SA Brown – Homicide Scene Processing
1759 Smith/ME Investigator Scene exam 1823
1800 H. Jones – CS Unit Scene Processing
1800 L. Marshall- CS Unit Scene Processing
1817 Chief Kyle Scene visit 1833
1817 Maj. Darren – PIO Update by Homicide 1833
The entry control log keeps track of who entered the scene, when,
why and when they left. It’s serves to validate scene integrity.

18. Crime Scene Team Approach
There are two approaches for creating crime
scene teams:
– By Area - single group of investigators is responsible
for all activity in the scene.
– By Function - specific groups are formed to handle
different scene processing aspects (e.g. photo team,
sketch team, latent team)
In normal scenes, custom and size of the
organization will often determine the approach.

19. Team Approach … continued
In complex scenes, issues of size or resources
may require the organization to alter its approach.
– Lack of equipment resources to handle multiple scenes,
may force a functional approach.
– If equipment resources are not an issue, but size is; area
teams may be necessary to handle small zones with in a
larger scene.
– The need for specialty examinations on scene may
force a functional approach.

20. Crime Scene Team Composition
Crime scene teams have to be manned
appropriately.
It is difficult to manage crime scene activity if the
teams are under staffed.
Different stages of the processing methodology
demand different levels of minimum manning.

21. Team Composition … continued
Photography teams require two individuals.
– One operates the camera.
– Second maintains the photo log and assists.
Sketch teams require three individuals.
– Two take measurements.
– One annotates the sketch and takes notes.
– In a pinch, two can do the job, but be careful as notes
and measurements get mixed up.

22. Team Composition … continued
Evidence Collection teams require two
individuals.
– One containerizes and physically collects the items.
– A second maintains the evidence log.
Search teams are a matter of circumstance, but
always require a minimum of two individuals.
– No two people survey or perceive the same way, so two
sets of eyes prevents items from being overlooked.

23. Search Considerations
Ultimately, some form of search must be
conducted at the scene to locate evidence.
The particular search pattern chosen is a function
of the situation.
No matter what search pattern is chosen the crime
scene team must decide on a search swathe size.

24. Search Swathe Size
The search swathe is the area that any given
searcher is viewing at any given moment in the
search.
How tight or how broad this search swathe will be
is a product of several considerations:
– Nature of the ground being searched.
– Lighting considerations.
– On-scene environmental conditions.
– Size of the item being searched for.

25. Terrain and Search Swathe Size
Terrain at Width 1 Terrain at Width 2
Terrain has a significant
affect on the size of
a search swathe.
Search Search
Width 1 Width 2
Area to be searched

26. Lighting and Search Swathe Size
Available lighting has a
significant affect on
the size of a search swathe.
Have alternate lighting systems available,
including: work lights and Alternate Light Sources
(ALS).

27. Environmental Conditions
Extreme heat or cold can affect the ability of the
searcher.
Wind, rain, fog and other factors may also impede
the searchers ability.
Any of these conditions may demand narrowing
the search swathe to preclude missing items.

28. Size of the Item Being Sought
In focused searches the size
of the item being sought can
affect the size of a search
swathe.
Sometimes we do directed searches, looking for a
specific object, which impacts our decisions.
It is one thing to look for a gun in the grass, its another to
look for a shell casing.

29. Search Patterns
There are five basic crime scene search patterns:
– Circle search.
– Strip or line search.
– Grid search.
– Zone search.
– Point to point search.
Each pattern works in a variety of circumstances,
but no single pattern works in every situation.

30. Circle (a.k.a. Spiral) Search
Excellent pattern in most interior or confined
exterior scenes.
Not effective in large exterior scenes or cluttered
areas that impact on the circular movement.
Searcher moves inward or outward from a starting
point.

31. Circle Search
End
End
Start
Narrowing Circle Widening Circle

32. Strip Search
Excellent in exterior scenes where a large area
must be examined.
Visual alignment to the strip is good for most
situations, but as the area to be searched grows, it
becomes more difficult to maintain a visual
reference of the lanes.
Physically laying out the strips with string or tape
can help maintain the order.

33. Strip Search
Start End

34. Line Search
Variation of the strip search, where multiple
searchers follow a single strip in one direction,
while on-line with each other.
Excellent for exterior scenes over rough terrain.
Usually requires supervisor(s) to maintain the
direction and alignment of the involved searchers.

35. Line Search
End Line
Start Line

36. Grid Search
The grid search is another variation on the strip
search.
Searchers follows strips in one direction, then
cuts across the scene in another set of strips,
oriented 90 degrees to the first.
Provides for multiple views of the same ground
by the same searcher from different perspectives.

37. Grid Search
End
Start

38. Zone Search
The zone search is used in several variations:
– To deal with small confined spaces where no patterned
search will work.
– To break a larger scene up into functional areas, that
are then searched using some other patterned technique.

39. Zone Search - Small Confined Areas
Zone G
Zone B Zone C
Zone J Zone F Zone E Zone H
Zone A Zone D
Zone I
An example is the car. No pattern search will work, so zones are
created that are searched individually.

40. Zone Search - Breaking Up a Larger Scene
Zone 6 Zone 5 Zone 4
Zone 7 Zone 9 Zone 3
Zone 8 Zone 1 Zone 2
An example is a home and the grounds. To keep perspective, the grounds
are broken up into zones, which are then searched individually using a
standard pattern technique.

41. Point to Point Search
Not widely used in the United States.
Searchers move from one focal point to the next,
creating cleared pathways to and from each.
They do not stray from these pathways.
Each focal point is dealt with before moving on to
the next.

42. Assessing Crime Scene Hazards
A variety of hazards to the crime scene
technician exist in the scene. These include:
– Bio-hazards from blood or body fluids.
– Structural hazards in fire and explosion scenes.
– Chemical and inhalation hazards in fire scenes.
– Inhalation and chemical hazards from on-scene
processing techniques.
– Inhalation and explosion hazards associated to drug
labs.
– Bio-chemical hazards associated with terrorism.

43. Crime Scene Hazards ... continued
Each scene must be assessed for any obvious
hazards.
Any risks associated to the hazard should be
mitigated, if possible, before exposing team
members to the hazard.
The use of personal protective equipment (PPE)
will mitigate or reduce exposure to many common
hazards (e.g. bio-hazards, chemical hazards)

44. Personal Protective Equipment
1. Goggles/eye protection - splash and
mucous membrane tissue protection. 1
2
2. Face/particle mask - inhalation
protection.
3
3. Tyvek suit - impervious to liquid
contaminants.
4
4. Rubber gloves - impervious to liquid
contaminants.
5. Booties - splash and contact protection
for footwear.
5

45. Media Issues
Assessment involves aspects of dealing with the
media (e.g. what information will be held back,
how much photo or video access will they get).
The media are often viewed in an antagonistic
fashion by the crime scene investigator.
Use caution when dealing with the media, but
treat them as professionals.

46. Media Issues … continued
Police are the gate-keepers. We decide how
much access to allow and what information to
release.
Don’t speculate, don’t lie and if you’re not
prepared to release information, then say so.
Assign experienced officers as the Public
Information Officer and then work as a team to
decide what information to release.