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 Teamwork

Leadership Employing the scientific method

Inductive and deductive reasoning Critically and creative thinking Communication with subordinates Logic and reasoning

Open mindedness Removed subjectivity and biases

“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.” – Chisum and Turvey

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 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

Formulate a hypothesis

Design experiment(s)

Perform the experiment(s)

Accept, reject, or modify the hypothesis

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

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

Common Examples of Bias

Case Example On Scene Case Bias and Incompetence

Brutal murder of a 20 year old woman Presumably by her ex-boyfriend

Case conclusion by investigating officers Ex-boyfriend breaks down glass door He grabs a chef’s knife and chases the ex-girlfriend upstairs He butchers the ex-girlfriend, - slashing her head and throat with the knife Stabs himself in the chest and leaves the bathroom

Other facts The ex-girlfriend’s sister calls her father who calls the police The father is first on the scene

He kicks the ex-boyfriend in the head He remains on scene during investigation

One of the officers on the scene is the uncle of the deceased He remains on scene during the investigation

The on-scene investigation is incomplete On-scene work was shoddy or simply not considered important

Photographs were not taken properly - without scales, without using a tripod or taken at an angle Bloody footprints were not enhanced properly

Case Example of Bias

Case Example of Bias

Logic & ReasoningDeductive reasoning General to Specific

Starts with a theory More structural

Inductive reasoning Specific to general

Begins with an observation

A theory is derived AND must be confirmed

More open ended

Theory

Hypothesis

Observation

Confirmation

TentativeHypothesis

Pattern

Observation

Deductive ReasoningInducti

ve Rea

soning

Theory

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?

Management Management is the glue that holds the investigation together

The manager = The team leader Success depends on leadership Learning to manage a crime scene is a critical skill

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 Training can be defective - perpetuate bad habits,

poor skills and faulty knowledge

Appropriate models of scene management do not exist

The First Responding Officer Scene management is an evolving or stepwise progression

Begins with the first official or responding officer to the scene

The responsibilities of the first responder: Preserve life Secure, preserve and protect the scene Document the scene as it was found until relieved by an investigator in

charge Hand off the scene to the investigator in charge via debriefing

A first officer’s responsibilities can be placed into discrete categories. Observations

What happened here? Who should respond?

Actions taken Documentation

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

Other Important Information

Second Level ObservationsArchive Observations: Digital or tape recording device, note pad, or point-and-shoot cameraCognizant 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 DO NOT

Move anything Touch anything Use the toilets Use the sinks Turn on water Eat or drink

All crime scenes are contaminated

The first officer: Must protect the scene until relieved by the investigator who assumes official responsibility for the subsequent on-going 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

Scene Security

Outdoor ScenesProtect entrance/exit points

Along paths, tire tracks on driveways, etc.Be cognizant of weather restrictionsCordon off large areas

Get help from othersEstablish boundaries

Witnesses and other voyeurs must be removed and segregated

The media is also a concern and 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

Official Busines

s

Scene&

Command Center

Official Busines

sSegregatedWitnesses

& PotentialSuspects

Media

Discrete Security Areas at the Scene

Public Public

Secure Travel Routes for Emergency Equipment / Personnel

Team Leader’s Role

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 OR move it to another location …

The same holds true for the media

Critical considerations

The team work area Establish command center Would certainly ruin footprints and fingerprints in those locations. Ensure the is media away from the main activity

An inexperienced responder may make mistakes 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

Crime Scene Investigative Team

Efficient ProcessingEvaluate time constraints

Scene location A hit-and-run on a major roadway

Weather. 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.

Scene processing responsibilities to be coordinated Must be completed within a reasonable period of

time and done correctly

Investigative Unit The investigator-in-charge is scene unit’s team leader

Ideally crime scene unit = 4 investigators + 1 team leader Comprised of both scientists and experienced officers

Unlike the “detectives” on CSI, no one person does it all Scene investigation is a team effort

Most crime scene units are comprised of police officers trained to process crime scenes

Some teams have criminalists Some have individuals with different backgrounds

Specialized expertise may be required Bones: Forensic Anthropologist Decomposing bodies: Forensic entomologist Bloodstain patterns: Forensic biologist/criminalist with

bloodstain pattern analysis (BPA) expertise Clandestine laboratory: Drug chemist

First Officer

Makes observationsSecures SceneSegregates witnesses/suspectsMedia issuesCalls appropriate agenciesDebriefs Team leader

Team Leader

Walk ThroughManages scene investigationConsiders legal concernsRe-checks FO’s decisions Determines the Scope of the SceneIntegrity/security/contaminationTeam RequirementsDevises investigation strategySearch StrategyPrepares reports/case files

Scene Investigation Sequence

Scene Investigation OverviewPhase I

Team LeaderOverview of

Responsibilities

Walk-through with FO Overview of scene Review Boundaries Identify fragile evidence

Design investigation plan Include a team buy-in strategy

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 highwayo Can only keep road closed for a short time

Homicide scene in the woodso Weather constraints

Political Considerations - Police shootingso Media & public attentiono Political fall-outo Community outrage

Apartment landlord wants to clean & re-rent Families want personal belongings

Clear Scene - Suspect @ scene Lawyers @ scene

o Prosecutorso Defense attorneys

Injured at the scene EMT

Deceased ME

Team Leader Overview of

Immediate Concerns

Managing The Scene

Establishing Teams

Teams Within the Crime Scene Unit

The team leader creates sub-teams Specific responsibilities for

processing certain aspects of the scene

Sub-teams have at least 1 member 1st sub-team might be a one-

person team who does all of the establishing photography

2nd sub-team might have two members that sketch, while another single member may be searching for evidence

Responsibilities may change as the scene investigation proceeds

Activity Checklist:Documenting

Archiving Logs

Evidence Scene attendance Photography Chain-of-custody

Evidence Search/PackageFingerprints

Locating/enhancing Photography Lifting/preserving

Bloodstains Presumptive/confirmative Testing Photography Pattern interpretation Enhancement

Shooting incidents Locating ballistic evidence Bullet Path Trajectories Position of shooter(s)

Reconstruction Hypotheses Testing

Case Files/Reports

Responsibilities of sub-teams: A two-member sub-team might be assigned to sketching then reassigned to searching for evidence, collecting and then packaging Another two-member team might be to photography then reassigned to the 2nd Touch phase (to be discussed) and then on scene processing The team leader could be performing the re-checks (to be discussed)

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.

Sub-Team Activities Example

Figure 3.4: Changing Sub-team Responsibilities in a 5-Member Unit

A Five Member Scene Unit

No 1 Two Member

TeamDocumenting

No 2 Two Member

TeamSearching

Team Leader 1st Re-check

Visual Inspection 1st Touch

Body Release

Impression Evid.Evidence Collection

Fingerprinting2nd Re-check

Protecting Evidence

Controlling EvidenceChain-of custody

Chain of custody (chain of evidence)Proof that evidence collected during investigation & evidence

submitted to the court are the sameProves integrity of the 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 observationso Scene building/room/furniture/fixtures/items present

This happens Prior to: Videography Photography Sketching Evidence not yet fixed

Scene Investigative Cascade

Fragile Evidence

Scene Investigative Cascade

Step 1: Pre-processing

Legal Issues

Debrief FO

Victims

Pre-processing Activity

1st Walk ThroughAfter pre-processing:

Team leader makes decisionsDebriefs their team Opportunity for CSU to walk-through the scene. Categorize the scene into its central theme: homicide, sexual assault, burglary, hit-and-run, mass fatality, etc.

Fragile Evidence

Scene Investigative Cascade

Step 2: Visual Inspection

Sketching

Video/Photography

Observations

1st Recheck

Visual Activity

Video completed Establishing Photography

completed Scene described in notes Scene Sketched or in

progress

Fragile Evidence

The Scene Investigative Cascade

Step 3: 1st Touch

Sketching

Video/Photography

Observations

1st Recheck

Evidence Collect

BodyRelease

2nd Recheck

Visual 1st Touch

More intensive Search – moving furnitureFingerprintingALS searchingCollecting/packaging Evidence – chain of custody

Separate butIntegral part of scene

The BodyMacroscene elementsBag hands & feetExamine with ALS

Fibers/blood drops/broken fingernails

Microscene elementsGSRBloodstain patternsPhotography

Critical review of what has taken place to this point.

Gives team second chance to see what, if anything has been missed

Reassess what else should be done.

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

Moving furniture

Looking for other evidence Proper documentation of these activities Found evidence will be marked, collected and packaged

2nd Re-check

Fragile Evidence

The Scene Investigative Cascade

Step 4: 2nd Touch

Sketching

Video/Photography

Observations

1st Recheck

Beyond

Evidence Collect

BodyRelease

2nd Recheck3rd Recheck

Wrap Up

Visual 1st Touch 2nd Touch

Chemistry

Footwear enhancementsBlood enhancementsSuperglue fumingLuminol sprayingOther needed procedures

After the chemical phase.

Final review to ensure that everything is completed.

Reminder that crime scenes may not necessarily be relegated to the immediate surroundings, e.g., the place where a body was found. Activity may have originated outside the set boundaries of the scene.

Scene Processing Cascade: Designed by the Military (non scientists) A road map to help prevent investigators from making critical mistakes Scientific method - feedback mechanism during 1st, 2nd, and 3rd re-

checks Criminalistic logic as embodied in the scientific method is missing

“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.”

Incorporating the scientific method helps to ensure that the investigation will be successful

Needs to be the foundation of the cascade Attempting to disprove your hypotheses

The Scene Investigative Cascade and The Scientific Method

Fragile Evidence

The Scene Processing Cascade

Incorporating the Scientific Method

Sketching

Video/Photography

1st Re-Check

Visual Activity

HypothesisRejectionTesting

1st Touch

Preprocessing

Re-Check 1A

HypothesisAcceptTesting

Fragile Evidence

First Officer

Makes observations Secures Scene Segregates witnesses/suspects Media issues Calls appropriate agencies Debriefs Team leader

Team Leader

Scene Investigation Sequence

Preprocessing Visual

Sketching

Photography

Observations

1st Recheck

1st Touch 2nd Touch

Evidence Collection

BodyRelease

2nd RecheckBeyond

3rd Recheck

Wrap Up

Scene Investigation Overview

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

chemistry

Scientific Method