Forensics, Observation, and Eyewitness Testimony in Crime Investigation

Forensics

The application of scientific techniques and principles to legal situations, using science to solve crimes

fact

a statement or observation that can be verified

opinion

a belief based on judgment rather than on direct experience or knowledge, bias

What is perception?

The process of interpreting sensory input.

How does the brain process sensory input?

The brain interprets sensory input through various processes.

What types of changes in perception are involuntary?

Opinions, judgment, and personal experiences.

What can affect the accuracy of perception?

Faulty interpretations can lead to inaccurate perceptions.

What is observation?

Information collected by the 5 senses or analytical techniques.

What are the 5 senses used in observation?

Smell, touch, taste, sight, and hearing.

What types of analytical techniques are used in observation?

Measurements, numbers, and units.

What is a potential issue with observation?

It is susceptible to subconscious filtering.

quantitative

(Microscopic analysis) analytical measurements, numbers and units, objective

qualitiative

(macroscopic analysis) general descriptions can contain bias, subjective

What can factors do to our observations

make it better or worse

the amount of activity

lots=worse

limited=better

the number of people

many= worse

few= better

nature of the activity

subtle=worse

disruptive=better

mood

happy=worse

nervous=better

extreme= terrible

being systematic

make a plan on how to observe, follow SOP, use a checklist, and observe with a pattern

What does it mean to document?

To write down information, take pictures, and record audio/videos.

Why is documentation important?

It ensures accurate, unbiased details are retained.

How does the brain affect memory?

The brain is faulty as it filters and interprets information.

do NOT filter

make a conscious effort to observe, turn your brain on, block out distractions, ensure no details are overlooked

What should you avoid while recording observations?

Bias

What should you deny from impacting the current situation during observations?

Previous experiences

Who is considered an eyewitness?

Any person who was present when the event took place, such as a victim, bystander, or accomplice.

What can impact an eyewitness's account of an event?

Bias and factors that impact observation skills, such as interest, focus, brain to memory, and time elapsed.

How are testimonies treated

as a fact, the actual event details vs opinion must be evaluated (background check, corroborate other evidence, does their testimony support or refute the "likely events")

What is a key characteristic of eyewitness memories?

Eyewitness memories are malleable and can be faulty or unreliable.

Can individuals control how they observe or remember events?

No, individuals cannot control how they observe or remember.

What do people tend to believe about their observations?

People tend to believe what they see or hear, even if it is not accurate.

How do legal professionals and juries typically view eyewitness testimony?

They often treat it as fact and find it highly persuasive.

What assumption is often made about eyewitnesses?

There is an assumption that eyewitnesses have no motivation to lie.

innocence project

exonerates the wrongly convicted through DNA testing and reforms the criminal justice system to prevent future injustice (if their incarceration was heavily based on eyewitness testimony)

CSI

A process were legal and scientific professionals work together to solve a crime and serve justice

Evidence

Any information or object that is associated or can be linked to the event

Primary evidence

Evidence that is transferred from the source to the location found

Secondary evidence

Evidence that is transferred from the source through at least one intermediate then to the location found

What is Locard's Exchange Principle?

The foundation of forensic science that states when two people, two objects, or a person and an object come into contact, material is exchanged.

What determines the amount of material exchanged according to Locard's Exchange Principle?

The nature, duration, and intensity of the contact.

Does the type of contact matter in Locard's Exchange Principle?

Yes, the type of contact affects the amount of material exchanged.

Police officer

Often the first responder, they secure and manage activity at the crime scene

Crime scene investigator

Manage how the evidence is collected and receive reports and manages the case

Medical examiner

Investigates a dead body performs an autopsy signs, death certificate determines cause, manner and mechanism of death

Detective

Will question/interview witnesses and suspects, follows leads and reports to the investigators

Forensic specialist

A specialist that is trained in one type of evidence analysis or specialized analysis technique,

Direct evidence

Supports an alleged fact, can be verified (eyewitness, video ,audio, photograph, confession ,court testimony)

Circumstantial evidence

Implies of fact, links, but does not prove, cannot verify when/how evidence was transferred

Class evidence

Narrows to a group of people that share the same characteristic

Individual evidence

Narrow to one person with that distinguishing characteristic

Physical evidence

Not derived from a living source, an impression or object

Biological evidence

Derived from a living source, human biological evidence

Trace evidence

Small but miserable, not visible with a naked eye, or requires specialized analysis

Not trace evidence

Typically larger, visible to the unaided eye, or easily collected or analyzed

Who is usually the first responder at a crime scene?

A police officer, fire department, or EMS.

What is one of the first actions taken by a first responder at a crime scene?

Secure the crime scene.

Why is it important to restrict access to a crime scene?

To reduce the possibility of contamination.

What should first responders do to ensure safety at a crime scene?

Document activity and call for backup or specific people who are needed.

What is the purpose of preserving information at a crime scene?

To maintain the integrity of the evidence.

Who is usually responsible for separating eyewitnesses at a crime scene?

The first responder

Why is it important to physically space eyewitnesses?

To avoid cross conversation and collusion

What can memory be affected by in eyewitness testimony?

Cognitive bias

What does separating eyewitnesses ensure during questioning?

More authentic information

Who can usually be the first responder at a crime scene?

The crime scene investigator

What is one of the first tasks at a crime scene?

Scan the crime scene

What should be identified at a crime scene?

Areas of interest

What must be determined regarding the processing of a crime scene?

Where more time plus effort is needed

What is the role of a forensics photographer at a crime scene?

To take photographs that document the scene.

What types of photographs should a forensics photographer take at a crime scene?

Close-up shots, wide shots, and special lighting shots.

Why should a forensics photographer use a ruler in photographs?

To provide scale and context for the objects in the scene.

What technique can be used to accurately document the positions of objects at a crime scene?

Triangulation.

What is the purpose of preserving the crime scene as discovered?

To avoid faulty memory and bias in later reconstructions.

Why is it important to document a crime scene for people who were not present?

To help them understand the scene and assist in reconstruction.

Sketch the crime scene

Forensic, sketch, artist, rough sketch, and a list of measurements are recorded at the crime scene, to compliment photographs while also including the entire layout of the scene to document the crime scene, avoid faulty memory

Search the crime scene

The investigator and possibly additional personnel, systematically using one of the search patterns, follow SOP place number cards near evidence that needs to be collected

Secure the evidence

The investigator or evidence collector

SOP standard operating procedure

a set of fixed instructions or steps for carrying out usually routine operations

dry

Bindle small objects, box large objects

wet

Allow to dry then package, avoid decomposition by microorganisms

Liquid

Sealed glass container