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Introduction to Forensic Science

Definition of Forensic Science

• Forensic: Pertaining to, or connected with, courts of law or public debate.
• Science: Knowledge of the physical world gained through observation.
• Forensic Science: The application of natural sciences to matters of law.

Fields of Forensic Science

1. Odontology: Examination of dental evidence, including bite marks.
2. Anthropology: Study of bones for forensic purposes.
3. Toxicology: Analysis of fluids or body tissues, particularly in cases of driving under the influence (DWI).
4. Biology: Examination of various body fluids.
5. Chemistry: Proving substances, such as identifying drugs from white powders.
6. Trace Analysis: Examination of glass, impressions, hairs, and fibers.
7. Ballistics: Analysis of casings and bullets.
8. Impressions: Typically under trace analysis, covering footprints, tire tracks, etc.
9. Questioned Documents: Examination of inks and identification of forgeries.
10. Forensic Photography: Documentation of various types of evidence.

Historical Development

• Forensic Medicine began in 6th-century China.
• 1880: Alphonse Bertillon developed anthropometry for identification.
• 1887: Sir Arthur Conan Doyle used scientific methods in investigations.
• 1892: Francis Galton conducted the first extensive study of fingerprints.
• 1901: Karl Landsteiner discovered four blood categories.
• 1910: Edmond Locard set up the first police lab in Europe, introducing the Locard Exchange Principle.
• 1985: Sir Alec Jeffreys applied molecular biology to forensic science, initiating DNA analysis.

Forensic Laboratories

• Federal Labs: FBI, DEA, ATF, US Postal Inspection Service.
• State Regional Labs: e.g., NJ (Eastern, Southern, Central Labs).
• Centralized Labs: e.g., CT (one forensic lab).
• Combination Labs: e.g., NY.
• County Labs: Union County Prosecutor’s Office, Westchester County Medical Examiner’s Office.

Functions of Forensic Scientists

• Apply scientific principles and techniques to evidence analysis.
• Follow the scientific method: observation, hypothesis, testing, theory.

Expert Witness

• Definition: A person with specialized knowledge relevant to a trial.
• Qualification: Must demonstrate expertise and competence.
• Distinction: Expert vs. Lay Witness.

The Forensic Scientist's Role

• Advocate for the truth.
• Unbiased analysis, drawing conclusions solely from evidence.

Physical Evidence in the Courtroom

• Frye Rule (1923): General acceptance of new procedures.
• Rule 702: A flexible standard (Strictly federal).
• Daubert Rule: Trial judge's responsibility for the admissibility and validity of scientific evidence.

The Crime Scene

Importance of the Crime Scene

• The primary source of physical evidence.
• Each scene is unique; careful processing is crucial.

Crime Scene Processing Guidelines

1. Secure and Protect:

   • Render first aid.
   • Apprehend the perpetrator.
   • Call the crime scene unit, supervisors, EMS.
   • Maintain control and isolate the scene.

2. Sort Relevant Items:

   • Distinguish between significant and insignificant items.

3. Normal vs. Abnormal Conditions:

   • Mental Reconstructions: Consider various scenarios.

4. Photography:

   • Overall Photographs: Document the entire scene.
   • Close-Up Photographs: Record details of specific items.

5. Sketches:

   • Rough Sketch: Initial draft of essential evidence.
   • Finished Sketch: Carefully drawn, includes all information for court use.

6. Notes:

   • General description, personnel present, date, time, location, and evidence.

7. Documentation:

   • Video Camera: Overall documentation.
   • Audio Recording: Detailed documentation during a walkthrough.

8. Search for Evidence:

   • Line Search, Grid Search, Zone Search methods.

9. Collection of Evidence:

   • Handle physical evidence to prevent alteration.
   • Packaging: Protect and preserve evidence.
   • Personal Protective Equipment (PPE): Use hairnet, face mask, jumpsuit, gloves, booties.

10. Crime Scene Safety:

    • Be cautious with sharp objects.
    • Consider the risk of diseases like Hepatitis transmitted through dried stains.

These guidelines ensure a thorough and systematic approach to crime scene processing, emphasizing the importance of accuracy and preservation of evidence.

Information from Physical Evidence

Purpose of Physical Evidence

• Prove Modus Operandi: Establishing the method of operation in a crime.
• Identify the Subject: Linking evidence to a specific individual.
• Exonerate the Innocent: Clearing individuals wrongly accused.
• Establish Linkage: Connecting suspects to victims or scenes.

Significance of Physical Evidence

• Identification:

  • Items are classified or categorized.
  • Requires using established tests with consistent results.

• Individualization:

  • Determines if evidence can come from a particular object or person.
  • Involves rendering an opinion about the common origin of known and unknown specimens.

• Comparison:

  • Subjects unknown and known specimens to the same tests.
  • Steps:
    1. Select meaningful characteristics.
    2. Draw conclusions about specimen origins.

Characteristics of Physical Evidence

Individual Characteristics

• Definition: Evidence associated with a common source with a high degree of certainty.
• Examples: Fingerprints, bullets, toolmarks, footwear impressions.

Physical Match

• Example: Matching glass or a headlight in a hit-and-run.

Class Characteristics

• Definition: Evidence associated with a group, not a single source.
• Examples: Paint, glass, fibers, soil.

Reconstruction

• Definition: Determining how a crime may have occurred based on observation and evaluation of physical evidence.
• Main Requirement: An undisturbed crime scene.

Indicators for Reconstruction

• Position of the body, location of bullets, presence of blood spatter, etc.

Radial Fractures

• Related to electron emissions.

Hairs and Fibers Trace Evidence

Locard Exchange Principle

• Definition: Anytime there is contact between two surfaces, there will be a mutual exchange of transfer or material.

Indications of Association

• Definition: Transfer of micro-environments with others.

Hair

• People lose 100-200 hairs a day.
• Hair is an appendage of the skin growing from the hair follicle.
• Hair shaft composed of cuticle, cortex, and medulla.
• Root goes through anagen, catagen, and telogen growth phases.
• Compound and comparison microscopes used for hair examination.
• Species Identification: Based on medulla and cuticle.

Fibers

• Divided into natural (animal or plant source) and manufactured.
• Natural Fibers: Derived from animal or plant sources (cashmere, wool, fur, cotton).
• Manufactured Fibers: Regenerated (rayon, acetate) or synthetic (nylon, polyester, acrylic).
• Microscopic comparison involves analyzing dye composition.
• Thin Layer Chromatography used for separating dye components.
• Fiber evidence may only provide class characteristics.

Drugs

Definition of Drugs

• Definition: Any natural or synthetic substances used to produce physiological or psychological effects.
• Categories: OTC, Rx, alcohol, nicotine, and controlled substances.

Controlled Substances

• Definition: Drugs or chemicals regulated by the government due to their effects on the central nervous system.
• Regulation: Covers manufacture, possession, and use.

Dependency

• Psychological Dependency:

  • Conditioned use of a drug driven by emotional needs.
  • Intensity varies based on the nature of the drug.
  • Examples: Alcohol, cocaine, heroin, nicotine.

• Physical Dependence:

  • Changes in the user's body that lead to a desire to continue using.
  • Discontinuation results in illness.

Types of Addiction

• Categories: Narcotics, hallucinogens, depressants, stimulants, club drugs.
• Examples: Marijuana (hallucinogen), alcohol (depressant), cocaine (stimulant), GHB (club drug).

Controlled Substances Act of 1970

• Purpose: Classified controlled substances into five schedules.

Fingerprints

Ridge Characteristics

• Definition: Features like islands, short ridges, ridge endings, bifurcation, and enclosure.
• Individuality: Identity, number, and relative location provide uniqueness.

Dermal Papillae

• Definition: Cells between the epidermis and dermis that determine ridge patterns.

Types of Fingerprints

• Latent Fingerprints:

  • Deposited by oil/sweat on fingers.
  • Have general ridge patterns: loop, arch, or whorl.

• Loops, Deltas, Whorls:

  • Radial Loop (opens toward thumb), Ulnar Loop (opens toward pinky), Deltas (triangles), Whorls.

• Arches:

  • Plain Arch (ridges rise like a wave), Tented Arch (ridges have a sharp spike).

• Double Loops, Accidental:

  • Two loops combined, or fingerprints not covered by other categories.

AFIS/IAFIS

• Definition: Automated Fingerprint Identification Systems for crime scene prints.

Bloodstain Pattern Analysis

Significance of Bloodstain Patterns

• Determinants: Location, position, and shape.
• Relevance: Indicates possible movements, positions of people, and event reconstruction.

Spatter Dynamics

• Result: Force interacting with a pool of blood.
• Determination: Direction and angularity of spatter.

Factors Influencing Bloodstain Patterns

• Surface Texture: Harder surfaces result in less spatter.
• Satellite Spatter: Occurs when droplets strike an object, distributing spatters.

Firearms, Tool Marks, and Other Impressions

Firearms

• Purpose: Determine if a bullet or cartridge was fired by a specific weapon.
• Technology: Integrated Ballistic Identification System (IBIS).

Forensic Serology

Definition and Scope

• Forensic Serology: Examination and analysis of biological evidence.
• Biological Evidence: Blood, semen, urine, vaginal secretions, fecal matter, saliva, sweat, nasal mucus.

Blood Components

• Cellular Portion: Red/white/platelets.
  • Red Blood Cells: Carry oxygen.
  • White Blood Cells: Fight infections.
  • Platelets: Assist in blood clotting.
• Liquid Portion (Plasma): Contains nutrients, antibodies, and proteins.