Scientific Method, Bias &
Reasoning
“Truth is sought for its own sake. And those who are engaged upon the quest
for anything for its own sake are not interested in other things.
Finding the truth is difficult, and the road to it is rough."
The hallmark of any successful crime scene investigation
 A team effort whose team leader, like the director of an orchestra, is its leader.
 How well the team performs is related to how well its leader employs the scientific
method, thinks critically and creatively, opens lines of communication with
subordinates, and employs inductive, deductive and abductive logic.
 If done properly the culture of science wraps its arms around the team and
protects it from making critical mistakes, introducing subjectivity, and from
conducting a biased investigation.
 This is true because science itself is self-correcting.
o Mistakes, when found are corrected, and biases, through the team effort and
the application of the scientific method, are avoided.
As Chisum and Turvey wrote
“Evidence interpretation is a complex process, and the less one understands
about the nature of physical evidence, the principles of forensic science,
analytical logic, and the scientific method, the simpler crime reconstruction may
seem.”
Crime Scene Investigation
More than the application of science
It is a complex scientific endeavor
A step-wise process of knowledge and information building.
 About understanding what happened
 Who might have done it and what probative evidence is there.
 Also a problem solving exercise.
 For example, why did this happen and in what sequence?
 Obtaining as precise an answer as possible illustrates why crime scene
investigation is particularly suited to the application of the scientific
method.
 The explanation of why this is true is clear.
 Just as scientists attempt to explain observations through a series of
constantly tested and revised hypotheses, the ultimate feedback
mechanism, using what is called the scientific method,
 So must scene scientists.
The Scientific Method
Observe a phenomenon that has no good explanation
(potential evidence, which we label as observable
phenomena).
 Formulate a hypothesis.
 Design experiment(s) to test the hypothesis.
 Perform the experiment(s).
 Accept, reject, or modify the hypothesis.
 Taken out of context, this list offers little insight
concerning how to apply the above to a specific scene
investigation.
Scientific Method in the News
“Scientists study the natural world to better understand it and to develop technology. Although many types of scientists study many aspects of the natural
world, they all follow the same step-by-step procedure to solving problems: the scientific method. By following this procedure, scientists ask questions and
conduct experiments according to a set of standards, with the goal of finding answers.
The process begins by asking a question: "Why does this work?" or "What happens if ...?" might spark a scientist's curiosity.
The research phase is next. To eventually answer their question, scientists must first study, and collect questions about, their topic of interest. They use
everything from their senses, to tools like microscopes, telescopes, computers or even particle accelerators.
Their sources for information can come from a wide range of places. Examples include personal knowledge, books, the Internet or interviews with scientists
and other knowledgeable people.
It's important to keep detailed records of all the information gathered during research because it enables scientists to form a hypothesis, or possible answer to
their question. The hypothesis is an educated guess based on your observations and your knowledge.
Once a hypothesis is developed, experiments are conducted to test its accuracy.
When developing experiments, many variables are considered. Variables are factors that may have a possible effect on the outcome of an experiment.
Scientists use controlled experiments that test individual variables.
For example, a hypothesis may be that germinated seeds need sunlight to grow into a plant. An experiment can be performed by placing one potted,
germinated seed near a source of direct sunlight and another potted, geminated seed away from direct sunlight.
A variable in this experiment can be fertilizer. Comparing a controlled group of fertilized plants to the unfertilized plants under similar conditions may make
the results of the experiment more valid. What other variables may affect the growth of seeds?
The next step in the process is observation. Scientists must keep accurate records of everything that occurred during the experiment. This data are then
evaluated and used in the conclusion of the process, to either support or oppose the hypothesis.
If this data disprove the hypothesis, more research is done to develop a new hypothesis and a new set of experiments.
If the data support the hypothesis, the final step is for the scientist to communicate the results. This is done in the form of a written report that describes the
results of the experiments and the conclusions drawn from the data.
Use the Internet to further research the scientific method. Then use the scientific method to answer questions about a topic you are interested in learning more
about. Be sure to keep detailed records of all of the information you gather during the process.”
New York Daily News, 2012 – “Science Funomena” page
Common Examples of Bias Affecting Forensic Investigations
Bias Example
Bias Description
Forensic Example
Bandwagon Effect
(also Groupthink, herd behavior,
manias)
Tendency to do (or believe
things because many other
people do (or believe)
The prosecutor or detectives are CERTAIN
a suspect is the killer because he is a “bad
guy.”
At the scene, this knowledge could sway the
course of the investigation especially if the
scene investigators know who the “bad
guy” is.
Confirmation Effects
The tendency to search for
or interpret information in a
way that confirms one's
preconceptions
The crime scene investigator who has a
preconceived idea of what happened or who
committed the crime and searches the scene
to uncover evidence to support that notion.
Observer-expectancy Effect
(also Observer Effects, Context
Effects, Expectancy Effects)
The expectation of a given
result with the unconscious
manipulation of an
experiment or
misinterpretation of data in
order to find it.
•An analyst expects a result but doesn’t get
it.
•Analyst creates scenarios so that the
correct results are not obtained.
•Crime scene investigator ignores evidence
that does not fit a specific theory of the case
Case Example
Brutal murder of a 20 year old woman, presumably by her ex-boyfriend is an example of extreme on-scene
bias and incompetence. The prosecutions alleged factual history:.
 Ex-boy friend breaks down glass door to the house to come after his ex-girlfriend, who is dating someone
else.
 He grabs a chef’s knife from a knife holder in the kitchen and chases the ex-girl friend to an upstairs
bathroom.
 He butchers the ex-girlfriend, slashing her head and throat with the knife.
 Stabs himself in the chest and leaves the bathroom, goes down the stairs and falls at the foot of the stairs
next to the kitchen where he remains until found by the police.
 The ex-girlfriend’s sister calls her father who calls the police.
 The father is first on the scene. He finds his daughter and then the ex-boyfriend. He begins kicking the exboyfriend in the head.
 One of the officers on the scene is the uncle of the deceased. He does not leave the scene.
 The father is still at the scene.
 The on-scene investigation is incomplete, presumably because the police conclude that the ex-boyfriend is
the murder.
 On-scene work was shoddy or simply not considered important since the “actor” was in custody.
 They photographed evidence the scene without scales and without using a tripod. Most photographs
were taken at an angle.
 Bloody footprints in the bathroom were not photographed properly nor were they enhanced,
Case Example of Bias
 Bloody footprints in the hallway in and outside the bathroom and in the
kitchen not enhanced or photographed properly.
 No on-scene comparisons were made of the class characteristics
footprint to the shoes of the deceased, the ex-boyfriend, or the father
No fingerprinting was performed at the scene.
 The ex-boyfriend’s clothing and shoes were not examined at the scene
or by the crime laboratory for glass shards.
 The bloodstain spatter patterns in the bathroom are not interpreted.
 A bloody knife found in the bathroom was processed by the police latent
print laboratory using amido black. Stained friction ridge detail is observed,
but the laboratory reports an inability to raise latent prints, photograph in
 BPA analysis of the staining on the knife does not support the contention that
the ex-boyfriend stabbed himself after murdering the ex-girlfriend.
Reasoning - Logic
A form of reasoning takes place during any crime scene investigation. And since crime scene
investigation is a scientific process … direct application of the scientific method implies logic
and reasoning.
Is The Scene Investigation a
deductive or inductive process?
Deductive reasoning
 Works from the general to the more specific and is often referred to as a “top-down”
process of logic.
 It begins with a theory, moves to a testable hypothesis.
 Testing or verification requires observations or experiments that address the hypothesis
which is ultimately either confirmed or not.
 This feels like what happens a crime scenes. Concerning deductive criminal profiling,
Brent Turvey says:
“The advantages of the Deductive Criminal Profiling model are very important. This model
requires specialized education and training in forensic science, crime scene reconstruction, and
wound pattern analysis. …
Deductive Criminal Profiles tend to be more specific than Inductive Criminal Profiles, assisting
greatly in the major goal of the profiling process, which is to move from a universal set of
suspect characteristics to a more unique set of suspect characteristics.”
Inductive reasoning
 Begins with an observation and moves to a testable tentative hypothesis,
 Is more open ended.
 This also feels like what happens at the crime scene.
 A theory is derived AND must be confirmed.
 In short, it moves from the specific to the general and is thought of as a
“bottom up” process of logic or reasoning. Concerning inductive criminal
behavior,
Turvey, says, inductive profiling is,
“The process of profiling criminal behavior, crime scenes, and victims from the
known behaviors and emotions suggested by other criminals, crime scenes, and/or
victims.
In essence, as the term suggests, this is reasoning from initial statistical data to
specific criminal offender behavior.
In any event, Inductive Criminal Profiling is generally the result of some kind of
statistical analysis, or finds it's reasoning in cases outside of the case at hand.”
De
Theory
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Hypothesis
t iv
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Observation
ea
son
ing
In
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ive
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ea
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Confirmation
Theory
Tentative
Hypothesis
Pattern
Observation
Management Basics: The Investigative
Glue
How many times have you read in the financial section of a newspaper
That the company failed because of poor management.
The team leader is the manager
 Success of the investigation depends on leadership. Management is the
glue that holds the investigation together
 Learning to manage a crime scene is a critical skill. Certain key factors
play interrelated and critical roles in successfully managed scene
investigations:
 Broad experience in scene investigation,
 Knowledge of police and legal procedures
 Knowledge of scene forensics/criminalistics, ,
 Understanding of the value of physical evidence,
 Knowing the limitations of the science,
 Applying the scientific method,
 Recognizing, collecting and preserving evidence,
 Management skills
 Know how to manage the scene.
 Know where to obtain scarce resources in unusual situations and
 Know how to expedite the investigation without compromising
quality.
Contemporary Problem
Rapidly changing dynamics of scene investigation related to
modern scene science and technology.
Firm foundation in science is a critical prerequisite for
successful scene investigations.
Crime scene team leader … regardless of the experience base
or the scientific backgrounds of the scene members, … must have
scene management expertise,
Investigation will fail or be botched, and critical evidence might
be lost forever.
Learning Scene Management
 Typically, learn scene management on-the-job or in police academies.
If the instructor is a world-class instructor with the correct knowledge
and experience, the training may top notch.
 If instructor learned on-the-job by an inadequate instructor, the
training can be defective because it can perpetuate bad habits, poor
skills and faulty knowledge.
 Appropriate models of scene management do not exist.
Investigators have been managing scenes for hundreds of years, and it
would be ludicrous to imply that none have been done correctly or to
suggest that all scenes have been managed correctly.
 Experience with four large police crime scene units, suggests that
many scenes are managed poorly.
The First Officer: Plays Critical Role
Scene management is an evolving or stepwise progression
 Begins with the first official or responding officer to the
scene.
 Most texts first explain the first responder’s responsibility
 Appropriate because first or responding officer usually first
official at scene.
 The role of this first responder is critical because he/she is
responsible to:
 Preserve life
 Secure, preserve and protect the scene
 Document as much as possible about the scene as it
was found until relieved by an investigator in charge.
 Hand off the scene to the investigator in charge via
debriefing.
The First Responder
Can dramatically affect the subsequent scene investigation.
A first officer’s responsibilities can be placed into discrete
categories.
 Observations
 Actions taken
 Documentation
 First level observations require the first office to answer
certain questions in order for the investigation to proceed
smoothly.
What happened here?
 Who should respond?

[1]
National Institute of Justice. The First Officer’s Responsibilities – 1995.
Other Important Information
 Is the scene active - is the perpetrator on the scene?
 Is the scene clear?
 Victims
 Injured & alive?
 EMS
Deceased?
 ME
 Witnesses/contact information
 Are there witnesses?
 Are they available?
 Are they separated/sequestered?
 Are the witnesses potential suspects?
 What is the scope of the scene?
 Boundaries
Indoor/outdoor/both
Second level observations
Reflect aspects of scene and include subtle details seen only after entering scene.
Archive Observations: Digital or tape recording device, note pad, or point-and-shoot camera.
Important as first seen information: Impressions and observations … not substitute for the subsequent official archiving by the crime
scene unit.
Cognizant of the following.
Fleeting evidence.
Odors – cooking, gunshot, cigarette/cigar smoke
Ice cubes melting
Entry/exit points
Doors – locked unlocked - tampered
Windows – locked unlocked - tampered
Signs of activity
Struggle
TV/radio on
Meals – dishes in the sink
Food on the table
Partially eaten food
Date/time indicators
Newspapers
Stopped clocks
Spoiled food
Hot/cold items
Wet blood
Other observations might include:
Account for moved or out of place objects (furniture)
Monitor evidence moved/altered by EMT’s as they attend to living victims
Protect obvious critical evidence
Fingerprints on dusty surfaces or dry residue prints on the floor or furniture
Cartridge cases
Spent bullets
Wet and dry residue footwear impressions
Broken glass
Major Do-Nots
Responding officers should be extremely careful that
evidence is not compromised, damaged or destroyed,
Generally, hands-off policy






Move anything
Touch anything
Use the toilets
Use the sinks
Turn on water
Eat or drink
Contamination: All crime scenes are contaminated
 1st Officer’s responsibility is to turn over to investigators as
virginal a scene as possible, which means protecting and securing
it properly.
Latent Fingerprint: The North American term for Latent Fingerprints found at scenes. Most of the rest of the world uses the term fingermark.
Scene Security
 Generalities exist:
 Murder in an apartment in a high-rise apartment building in New
York City different than one in a field where a small plane crashed.
 The first officer: Must protect the scene until relieved by the
investigator who assumes official responsibility for the subsequent ongoing investigation.
 With respect to security, the following are possible considerations for
indoor scenes:




Establish scene boundaries
Protect possible entrance/egress points
Protect possible probative evidence or evidence location points
Protect potentially fragile evidence
Outdoor Scenes
 Protect entrance/exit points
 Along paths, tire tracks on driveways, etc.
 Be cognizant of weather restrictions
 Cordon off large areas
 Get help from others
 Establish boundaries.
 Witnesses and other voyeurs must be removed.
 The media is also a concern. It should be removed from the
scene
 Sophisticated listening devices cannot hear discussions
among investigators
 Powerful cameras cannot grab photographs of salacious
material
 Dead bodies do not end up on the evening news.
Establishing Boundaries
Discrete Security Areas at the Scene
Public
Segregated
Witnesses
&
Potential
Suspects
Official
Busines
s
Official
Busines
s
Media
Scene
&
Command Center
Secure Travel Routes for
Emergency Equipment / Personnel
Public
Team Leader’s Role
Enter the Crime Scene Investigative Team
 Team leader picks up where 1st officer left off.
If additional preliminary work is needed, NOW is when to do it.
 Neglected to set aside space for the command center:
 Consider the most appropriate location. Should be unit discussion.
 OR move it to another location … The same holds true for the media.
Critical considerations.
 The team work area: Close but not where team members can possibly ruin
evidence.
 Command center: Ideally should not require investigators to trample though the
entrance or egress points
 Would certainly ruin footprints and fingerprints in those locations.
 Keep Media from the main activity of the investigation.
 An inexperienced responding makes mistakes
 May place the media too close to the investigative activity.
 Choose improper place for command center
 Fail to segregate witnesses
 Fail to inform other investigative personnel
Efficient Processing of the Scene,
 Time constraints. Evaluate carefully for effect on the ability to effectively and
efficiently complete investigation.
 Scene location.
 A hit-and-run on a major roadway, blocking it may be impossible and involve
political aspects out of the team leader’s control
 Weather.
 A homicide in the woods where there is threat of rain, forces team leader to
consider how to protect fragile evidence. Or the team leader might order large
tents to protect areas of the scene so that the team can complete the
investigation without rushing.
 Considerations BEFORE the team sets foot in the scene.
 Specific scene processing responsibilities to be coordinated and addressed from
within the constraints of the scene itself.
 Like all scene activity, these must be completed within a reasonable period of time
and done correctly
Turning Over The Scene to Investigative Unit
After the official transfer of scene control, time to begin the systematic and
analytical process of ascertaining what the scene offers in evidentiary terms.
DEFINE:
The investigator-in-charge is scene unit’s team leader.
 Unlike the “detectives” on CSI, no one person does it all.
 Scene investigation is a team effort, the composition determined by the
scene itself and the resources available.
 Most crime scene units are comprised of police officers trained to
process crime scenes. Some teams have criminalists. Some have
individuals with different backgrounds.
Sometimes additional specialized expertise is required.
Additional Expertise
Bones: Forensic Anthropologist - not usually a member of
responding team.
Decomposing bodies: Forensic entomologist may be
required, and
Bloodstain patterns: Forensic biologist/criminalist with
bloodstain pattern analysis (BPA) expertise should be called,
Clandestine laboratory: Drug chemist.
Scene Investigation Overview
Phase I
First Officer
Makes observations
Secures Scene
Segregates witnesses/suspects
Media issues
Calls appropriate agencies
Debriefs Team leader
Team Leader
Walk Through
Manages scene investigation
Considers legal concerns
Re-checks FO’s decisions
Determines the Scope of the
Scene
Integrity/security/contamination
Team Requirements
Devises investigation strategy
Search Strategy
Prepares reports/case files
Scene Investigation Sequence
 Walk-through with FO
 Overview of scene
 Review Boundaries
 Identify fragile evidence
 Design investigation plan
 Include a team buy-in strategy
Team Leader
Overview of
Responsibilities
 Determine the Archival Sequence
 Video
 Photography
 Sketching
 Identify On-scene Issues






Protect fragile evidence
Search the scene
Collect evidence
Dust/enhance prints
Other chemistries
Consider other scenes
 Consider Event Reconstruction
 Case file management
 Crime scene report
 Establish Command Center
 Review Media Considerations
 Constraints & Other Concerns
 Time constraints
 Hit-and-run on highway
o Can only keep road closed for a short time
 Homicide scene in the woods
o Weather constraints
Team Leader’s
Immediate Concerns
 Political Considerations - Police shootings
o Media & public attention
o Political fall-out
o Community outrage
 Apartment landlord wants to clean & rerent
 Families want personal belongings
 Clear Scene - Suspect @ scene
 Lawyers @ scene
o Prosecutors
o Defense attorneys
 Injured at the scene
 EMT
 Deceased
 ME
Managing The Scene
Establishing Teams
Teams Within the Crime Scene Unit
Theoretically: No correct way to investigate a scene …
certainly incorrect ways.
The team leader creates sub-teams,
 specific responsibilities for processing certain
aspects of the scene.
Sub-teams may have one or more members
 1st sub-team might be a one-person team who does
all of the establishing photography.

sub-team might have two members that sketch,
while another single member may be searching for
evidence.
Activity Checklist
•
–
–
Archiving
Logs
•
•
•
•
•
•
•
–
–
–
Locating ballistic evidence
Bullet Path Trajectories
Position of shooter(s)
Reconstruction
–
–
•
Presumptive/confirmative
Testing
Photography
Pattern interpretation
Enhancement
Shooting incidents
–
–
–
•
Photography
Lifting/preserving
Bloodstains
–
•
Evidence
Scene attendance
Photography
Chain-of-custody
Evidence Search/Package
Fingerprints
– Locating/enhancing
–
–
2nd
 As the scene processing continues, the
responsibilities of these sub-teams and their individual
members might change as the scene investigation
proceeds.
Documenting
Hypotheses
Testing
Case Files/Reports
Sub-Team Activities
 Responsibilities of sub-teams: Composition can change.
 A two-member sub-team might be searching for evidence, collecting and
packaging
 The team leader could be performing the first re-check (discussed below) and
 Another two-member team might be beginning the 2nd Touch phase (discussed
below) and begin dusting for fingerprinting on walls, door knobs, etc.
 When the first two-member team finishes sketching, it might be assigned to
the 2nd re-check.
 Minimum number of team members: 3 including the team leader.
 If the team had five members, two-member sub-teams would perform specific
tasks, moving from one activity to another, and the team leader would monitor
and perform specific duties as well.
A large team might have five members which could have
the sub-team responsibilities split as follows.
Figure 3.4: Changing Sub-team Responsibilities in a 5-Member Unit
A Five Member Scene Unit
Visual Inspection
No 1 Two
Member
Team
Documenting
No 2 Two
Member
Team
Searching
Team
Leader
1st Re-check
1st Touch
Fingerprinting
2nd Re-check
Impression Evid.
Evidence Collection
Body Release
Protecting Evidence
Controlling Evidence
Chain-of custody
Chain of custody (chain of evidence)
 Proof that evidence collected during investigation & evidence
submitted to the court are the same
 Proves integrity of the PE
 Identifying information on ALL packaging
 Name/initials of individual collecting the evidence
 Each person subsequently having custody of it




Dates item collected or transferred
Agency, case number, type of crime
Victim and/or suspect’s names
Brief description of the item
Documenting Observations
Investigator’s notes
 Can use recording device
 Transcribe ASAP
 Must use handwritten notes
 Detailed observations
o Scene building/room/furniture/fixtures/items present
 This happens Prior to:




Videography
Photography
Sketching
Evidence not yet fixed
Scene Investigative Cascade
The Scene Investigative Cascade
 Investigative Process: Takes place in logical steps so that
important evidence is not missed, damaged, or obliterated.
 1st visit to scene: No guarantee that investigation is completed.
Not unusual for a crime scene team to re-visit a scene several
times.
 Questions arise … additional theories proffered that question
the original investigation.
 Therefore, the scene must be thoroughly archived to preserve
the initial scene.
Cascade of Logical Sequential Steps.
Step 1: Pre-Processing (Investigation)
 First, pre-processing: Before the crime scene unit members set eyes or feet
on the scene.
 Essentially 1st Officer turning the scene over to the team leader.
 Visual Inspection. Here only visual observations are made which will be
translated into future action.
 This is when the scene is archived for posterity, including: written or
recorded observations, photography (and/or videography), and sketching .
Scene Investigative Cascade
Step 1: Responding Officer
Pre-processing Activity
Legal Issues
Debrief FO
1st Walk Through
Fragile
Evidence Victims
After pre-processing:
Team leader makes decisions, some
of which will be made after a meeting
with the crime scene team and the team
has an opportunity to walk-through the
scene.
 Categorize the scene into its central
theme: homicide, sexual assault,
burglary, hit-and-run, mass fatality, etc.
Second Step
Visual Inspection
 Only visual observations made: Translated into future action. This is when
the scene is archived for posterity, including: written or recorded observations,
photography (and/or videography), and sketching .
1st Re-check is critical because this is when the team – or team leader –
reviews what has been done and checks to see what might have been
missed.
Still a visual process. Nothing is touched – except perhaps for fragile
evidence - but evidence that had been missed initially must be
documented as though being catalogued for the first time, which it is.
The scene is described in notes or digitally and the overview photography
and sketching is complete.




Video completed
Establishing Photography completed
Scene described in notes
Scene Sketched or in progress
The Scene Investigative Cascade
Step 2: Team Leader
Visual Activity
Observations
Video/Photography
Fragile
Evidence Sketching
 Video completed
 Establishing Photography
completed
 Scene described in notes
 Scene Sketched or in
progress
1st Recheck
Step Three
1st Touch
 1st time hands actually touch anything.
 The team may leader release the body,
 Only after the team considers it as a scene unto
itself
 Archiving, etc (within the context of the entire
scene has been completed).
 Observed evidence during the Visual Inspection
phase will have been documented using video,
photography, and by sketching, etc.
The Scene Investigative Cascade
Step 3: 1st Touch
1st Touch
Visual
Observations
Video/Photography
Fragile
Evidence Sketching 1st Recheck
The Body
Macroscene elements
Bag hands & feet
Examine with ALS
Fibers/blood drops/broken
fingernails
Microscene elements
GSR
Bloodstain patterns
Photography
Body
Release
Evidence
nd
Collect 2 Recheck
Separate but
Integral part of scene
Critical review of what
has taken place to this
point.
Gives team second
chance to see what, if
anything has been
missed
More intensive Search – moving furniture Reassess what else
should be done.
Fingerprinting
ALS searching
Collecting/packaging Evidence – chain of custody
Simultaneous Activities in Step 3
Sub-teams are performing multiple tasks
 Finding and lifting fingerprints on walls and other surfaces,
 Examining footwear impressions to determine whether they have a dry
or wet origin and the team leader might be moving furniture
 Looking for other evidence.
 Midrange and close-up photographs document these activities.
 Found evidence will be marked, collected and packaged. And
finally, one or more members of the unit will perform the …
 2nd Re-check,
Step Four
2nd Touch
Chemistry phase
 Chemical enhancements of bloodstains, super glue fuming of prints that
cannot be removed from the scene, bullet path determinations and bloodstain
pattern area of origin determinations are performed.
 Activities are performed last because the evidence associated with these
activities is generally not fragile and will not be obliterated or destroyed
during the previous scene activity.
 Critical that these activities completed: photographing bloody shoeprints
before and after enhancement, photographing super glue fumed prints after
visualization, etc.
3rd Re-check,
The Scene Investigative Cascade
Step 4: 2nd Touch
1st Touch
Visual
Observations
2nd Touch
After the chemical phase.
Video/Photography
Fragile Sketching
Evidence
st
Final review to ensure that
everything is completed.
1 Recheck
Body
Release
Evidence
Collect
2nd Recheck
Chemistry
3rd Recheck
Footwear
Beyond
enhancements
Wrap Up
Blood enhancements
Superglue fuming
Luminol spraying Reminder that crime scenes may not necessarily be
relegated to the immediate surroundings, e.g., the place
Other needed
where a body was found. Activity may have originated
procedures
outside the set boundaries of the scene.
Step Four – Sequence Continued
Beyond.
 After the 3rd Re-check,
 The driveway - tire tracks.
Fingerprints - on windowsills.
 Why boundaries were established
at the outset of the investigation.
 The surrounding area must
be checked as though it was an
independent scene: video,
photography, sketching,
searching, collecting,
packaging, chemistry, etc.
Wrap-up.
 After the 3rd Re-check
 Team wraps-up the investigation,
and
 Team leader then considers
whether to release the scene.
 The entire investigative sequence,
absent the rigor of the scientific
method is shown in the following
graphic.
 Debrief team


Review checklists
Collect documents




Chain-of-custody
Notes
Sketches
Memory cards
 Release or Secure Scene

Make a decision whether to release
or keep the scene
 Process and Package Evidence

At headquarters
 Dry wet blood evidence
 Package other evidence
 Formal debriefing

Within 24 hours
Integrating the Cascade
with the Scientific Method
 Scene Processing Cascade: Designed by the Military …
investigators can work the scene without making critical mistakes.
 Suggests scientific method involvement as feedback
mechanism
during 1st, 2nd, and 3rd re-checks.
 Criminalistic logic as embodied in the scientific method is
missing.
 Incorporating the scientific method ensures that any
investigation will be successful.
Why the Cascade Works
 Cascade works because of re-checks.
 Not an unreasonable approach for
nonscientists.
 NOT sufficient & can be made better
 The scientific method should be the bedrock of
the investigation & should be integrated into the
Cascade
“Criminalistics is an holistic process that embraces
the scientific method, reasoning and critical thinking
with respect to the analysis and interpretation of
evidence associated with an set of alleged facts.”
The Scene Processing Cascade
Incorporating the Scientific Method
Preprocessing
Visual Activity
Video/Photography
Fragile
Evidence
Sketching
1st Re-Check
Rejection
Testing
Hypothesis
Re-Check 1A
1st Touch
Accept
Testing
Hypothesis
Scene Investigation Overview
First Officer






Makes observations
Secures Scene
Segregates witnesses/suspects
Media issues
Calls appropriate agencies
Debriefs Team leader
Team Leader









Walk Through
Manages scene investigation
Considers legal concerns
Re-checks FO’s decisions
Scope of the scene
Integrity/security/contamination
Team Requirements
Devises investigation strategy
Search Strategy
Prepares reports/case files
Scene Investigation Sequence
Preprocessing
Visual
Observations
Photography
Fragile
Evidence Sketching
1st Touch
Body
Release
Evidence
Collection
2nd Touch
chemistry
3rd Recheck
Beyond
2nd Recheck
Wrap Up
1st Recheck
Scientific Method