Forensic Science: Observation and Evidence Collection

Observation

The act of noting and recording facts and occurrences, often using your senses. It involves the careful attention to detail in order to gather accurate information.

Brain Changes While Observing

The brain processes incoming information through various sensory pathways (sight, sound, touch, etc.). When focusing on something, the brain releases neurotransmitters like dopamine and serotonin, which can affect concentration and memory. Stress or fear can also affect the reliability of what is observed.

Factors Influencing Eyewitness Accounts

Stress, anxiety, lighting, distractions, the witness's emotional state, and the passage of time can all impact the accuracy of eyewitness testimony. Memory can also be altered by outside influences like leading questions or suggestions.

Eyewitness Testimony vs. Actual Events

Eyewitness testimony can be unreliable due to various factors like perception, memory decay, and biases. In contrast, physical evidence (such as DNA or fingerprints) provides more objective information about the actual events.

Observation Skills in Forensic Science

In forensic science, observation skills are crucial for identifying evidence, analyzing crime scenes, and reconstructing events. The ability to notice and correctly interpret details directly affects the outcome of investigations.

Forensic Science

The application of scientific methods and principles to solve crimes. It involves the collection, analysis, and interpretation of physical evidence found at crime scenes.

Improving Observation Skills

Techniques such as mindfulness, focusing attention, avoiding distractions, and practicing memory recall exercises can help enhance one's observation skills.

Locard's Principle of Exchange

"Every contact leaves a trace." This principle asserts that when two objects come into contact, they exchange material that can be used as evidence. This exchange could involve hair, fibers, fingerprints, or other substances.

Four Examples of Trace Evidence

Hair, Fibers, Glass, Soil

Direct vs. Circumstantial Evidence

Direct Evidence: Evidence that directly proves a fact (e.g., a witness's testimony or a video recording). Circumstantial Evidence: Evidence that suggests a fact but does not directly prove it (e.g., a suspect's fingerprints at the scene or a footprint leading away from a crime).

Seven S's of Crime-Scene Investigation

1. Secure the Scene: Ensure the area is safe and preserve evidence. 2. Separate the Witnesses: Prevent witnesses from discussing the event. 3. Scan the Scene: Survey the scene to determine where evidence might be. 4. See the Scene: Look for evidence and take photographs of the scene. 5. Sketch the Scene: Draw a diagram showing important evidence and its layout. 6. Search for Evidence: Carefully search for evidence in a systematic manner. 7. Secure and Collect Evidence: Collect evidence following strict procedures to avoid contamination.

Securing the Crime Scene

Securing the crime scene is critical to ensure that no evidence is lost, destroyed, or contaminated. The area must be isolated and guarded to protect evidence from being tampered with or altered.

Methods of Documenting a Crime Scene

Photography, Sketching, Notes (detailed descriptions of the scene and evidence)

Mapping a Crime Scene

Mapping involves measuring and recording the location of key evidence and objects found at the scene. This often includes creating a scaled diagram or map to show spatial relationships between items and areas of interest.

Hair Follicle

The part of the hair that is embedded in the skin.

Hair Shaft

The visible part of the hair that protrudes from the skin.

Medulla

The innermost layer of the hair shaft, which may be continuous, fragmented, or absent.

Cortex

The thick middle layer of the hair that contains pigment and provides strength.

Cuticle

The outer layer of the hair, made up of overlapping scales.

Medulla (Variations)

Can be continuous, fragmented, or absent. Its pattern is unique to individuals and species.

Cortex (Variations)

Contains pigment (melanin), which gives the hair its color. The cortex also varies in texture and structure.

Cuticle (Variations)

The scales of the cuticle are distinctive and can help identify the species of origin.

Human Hair

Generally has a narrower medulla and more uniform pigment.

Animal Hair

Typically has a thicker medulla and more variation in color.

Using Hair in Forensic Investigation

Hair can be used to determine species, identify individuals, or link suspects to crime scenes. It can be compared microscopically or chemically analyzed for DNA.

Distinguishing Hair from Broad Racial Categories

Hair from different racial groups (Caucasian, African, Asian) exhibits distinctive characteristics, such as the shape of the hair shaft, texture, and patterns in the medulla.

Physical Analysis (Fibers)

Involves examining the shape, size, and appearance of fibers.

Chemical Analysis (Fibers)

Identifies the chemical structure of fibers through techniques like chromatography or spectroscopy.

Cotton

A natural fiber, soft, and flexible, made from the cotton plant.

Wool

A natural fiber from sheep, used in textiles for warmth and durability.

Silk

A natural fiber produced by silkworms, valued for its softness and sheen.

Asbestos

A naturally occurring mineral fiber, historically used for its fire-resistant properties but now known to be toxic.

Characteristics of Fingerprints

Fingerprints are unique to each individual and consist of ridges, furrows, and minutiae points (like bifurcations and ridge endings).

Loop (Fingerprint Type)

A fingerprint pattern where the ridges flow in one direction and then curve back.

Whorl (Fingerprint Type)

A circular or spiral pattern in the fingerprint.

Arch (Fingerprint Type)

A pattern where the ridges flow from one side to the other, without looping back.

Automated Fingerprint Identification Systems (AFIS)

A digital database for storing and comparing fingerprint data.

Latent Print Enhancement

Techniques such as dusting or chemical treatments to reveal invisible fingerprints.

Determining if a Fingerprint Matches

Fingerprints are compared by analyzing minutiae (unique ridge patterns), ridge counts, and overall shape.

Lifting a Latent Print

A technique to collect fingerprints that are not visible to the naked eye, using powders, tape, or chemicals to lift the print from a surface.

Forensic

Related to the application of science to law and criminal investigation.

Fact

An objective truth or reality, something that can be verified.

Opinion

A personal belief or judgment that is not based on facts.

Perception

The way an individual interprets or understands information or events.

Eyewitness

A person who directly observes an event, such as a crime, and can testify about it.

Analytical Skills

The ability to analyze and break down complex information into understandable parts.

Deductive Reasoning

A method of reasoning where a conclusion is reached by examining premises that are generally accepted as true.

Circumstantial Evidence

Evidence that implies a fact but does not directly prove it.

Class Evidence

Evidence that can be linked to a group but not to a single individual.

Crime-Scene Investigation

The process of examining and analyzing a crime scene to gather evidence.

Direct Evidence

Evidence that directly proves a fact, such as a video or eyewitness testimony.

Individual Evidence

Evidence that can be linked to a single individual, like DNA or a unique fingerprint.

Trace Evidence

Small pieces of evidence that can be transferred between individuals or objects, such as hair or fibers.

Locard's Principle of Exchange

The theory that when two objects come into contact, they exchange material.

Cortex

The middle layer of hair that contains pigment and provides strength.

Cuticle

The outer layer of the hair shaft, consisting of overlapping scales.

Hair Follicle

The part of the hair embedded in the skin from which hair grows.

Hair Shaft

The visible part of the hair that extends from the follicle.

Keratin

A protein found in hair, skin, and nails, providing structural strength.

Medulla

The innermost part of the hair shaft, which can vary in appearance.

Melanin Granules

Pigments found in the hair cortex that give hair its color.

Direct Transfer

The transfer of evidence directly from one object or person to another.

Secondary Transfer

The transfer of evidence from one person/object to another via an intermediate object/person.

Fiber

A thin, thread-like piece of material that can be used as evidence in forensic investigations.

Monomer

A single molecule that can bond with other molecules to form a polymer.

Polymer

A large molecule made from repeating units of monomers.

Natural Fiber

Fibers derived from natural sources such as plants or animals (e.g., cotton, wool).

Synthetic Fiber

Fibers made from artificial materials, typically petroleum-based (e.g., polyester).

Warp

The longitudinal threads in woven fabric.

Weft

The crosswise threads in woven fabric.

Yarn (Thread)

A long strand of fibers twisted together to form fabric.

Arch

A fingerprint pattern where the ridges flow from one side to the other without looping back.

Core

The central area of a fingerprint pattern.

Delta

A triangular pattern found in fingerprints, where ridges converge.

Fingerprint

The unique pattern of ridges and furrows on the tips of fingers.

IAFIS

The Integrated Automated Fingerprint Identification System, a digital database used for fingerprint matching.

Latent Fingerprint

A fingerprint left on a surface that is not visible without enhancement.

Loop

A fingerprint pattern where the ridges flow in one direction and then curve back.

Minutiae

Specific ridge patterns found in fingerprints, including ridge bifurcations and endings.

Patent Fingerprint

A visible fingerprint left on a surface after the finger comes into contact with a substance like ink or blood.

Plastic Fingerprint

A 3D fingerprint left in a soft substance like clay or wax.

Ridge Count

The number of ridges between two points in a fingerprint, often used for identification.

Ridge Pattern

The overall pattern of ridges in a fingerprint (loop, whorl, or arch).

Ten Card

A card used to record and categorize an individual's fingerprints.

Whorl

A fingerprint pattern that forms a circular or spiral shape.