FORENSIC SCIENCE DOC

General Information About Forensic Science

  • NE-DO NOT CROSS CRIME SCENE

History & Development of Forensic Science

  • Criminalist: Forensic Scientist

  • TV Forensics vs Real Forensics: Comparison

    • Interrogate suspects and kick down doors (TV)

    • Never interrogate suspects; mostly respond to crime scenes after the fact (Real)

    • Make judgments about guilt/innocence (TV)

    • Should avoid judgments; may compromise impartiality (Real)

    • Act independently of other investigators (TV)

    • Work as part of an investigative team (Real)

    • Operate as part of a team usually in a subordinate role (Real)

    • Have multiple expertise (TV)

    • Usually specialized without multiple expertise (Real)

    • Deal with observable and quantifiable phenomena (Real)

    • Get DNA results within a day (TV)

    • DNA results average 2-3 weeks (Real)

Important Figures in Forensic Science

  • Sir Arthur Conan Doyle:

    • Creator of Sherlock Holmes; pioneered concepts like

    • Serology

    • Fingerprinting

    • Firearm identification

    • Document examination

    • Published A Study in Scarlet (1887)

  • Mathieu Orfila:

    • Father of forensic toxicology; published works in 1814.

  • Alphonse Bertillon:

    • Developed anthropometry, a system of body measurements for identification.

  • Francis Galton:

    • Conducted first definitive study and classification of fingerprints (1892).

  • Leon Lattes:

    • Determined blood groups from dried blood (1915).

  • Hans Gross:

    • Suggested combining police investigations with scientific method (1893).

  • Calvin Goddard:

    • Known for ballistics; matching bullets to firearms.

  • Albert Osborne:

    • Focused on document examination (1910).

  • Edmond Locard:

    • Influenced by Gross and Doyle; established scientific methods for crime scenes.

    • Founded the first crime lab.

FBI Contributions

  • FBI Laboratory Establishment (1932):

    • Under J. Edgar Hoover, aimed to serve all law enforcement agencies.

    • Largest forensic lab in the world, conducting over one million exams annually.

  • FBI Forensic Science Research and Training Center (1981):

    • Develops new scientific methods in forensic science.

    • Provides training for crime lab personnel.

Crime Lab Services

  • Types of Services Provided:

    • Physical science

    • Biology

    • Firearms

    • Document examination

    • Photography

    • Fingerprints

    • Ballistics

    • Polygraph

    • Voice analysis

    • Evidence collection

    • Trace evidence

    • Arson

    • Toxicology

    • Computer crimes

  • Scientific Forensic Services:

    • Pathology

    • Anthropology

    • Entomology

    • Psychiatry

    • Odontology

  • Other Scientific Fields:

    • Engineering

    • Accounting

    • Chemistry

    • Biology

    • Botany

Legal Standards for Evidence

  • Frye vs United States (1923):

    • Established a standard for admissibility of scientific evidence in court.

    • Requires techniques to be “generally accepted” in the relevant scientific community.

  • Daubert vs Merrell Dow Pharmaceuticals (1993):

    • Set guidelines for scientific evidence based on reliability and relevance of methodology.

  • Admissibility Considerations by Judges:

    • Evidence testing

    • Peer review

    • Error rates

    • General acceptance in scientific areas.

Expert Witness Testimony

  • Qualifications to be an Expert Witness:

    • Education/higher degrees

    • Relevant experience

    • Publications

    • Affiliations with professional organizations

  • Voir Dire Process:

    • A procedure to establish an expert’s qualifications.

Crime Scene Investigation

  • Importance of Scene Management:

    • The integrity of evidence is paramount; incorrect handling can ruin a case.

    • Focus on observable phenomena, details of what is present and absent.

Types of Crime Scenes

  • Outdoor Crime Scenes: Can vary in size dramatically (small areas to several miles).

  • Indoor Crime Scenes: Easier to manage, but may be crowded with personnel.

  • Conveyance Crime Scenes: Related to transportation.

Types of Crime Scenes Described:

  • Primary Crime Scene: The main location of the crime.

  • Secondary Crime Scene: Any location connected to the crime.

Crime Scene Investigation Process Steps:

  1. Recognition: Survey, document, and collect evidence.

  2. Identification: Comparison testing and analysis.

  3. Individualization: Evaluation and interpretation of evidence.

  4. Reconstruction: Reporting and presenting findings.

Securing the Crime Scene

  • Initial Actions:

    • Secure the scene for safety, medical assistance, and establishing a perimeter.

  • Walk-through Methodology:

    • Record preliminary observations and photography (overview and close-ups).

  • Documentation Tools:

    • Photography, sketching (rough and finished), note-taking.

Evidence Collection Practices:

  • Search Methods:

    • Patterned search for evidence.

  • Packaging Guidelines:

    • Use dry paper bags for evidence storage (except for arson evidence).

    • Maintain chain of custody in documentation.

  • Legal Considerations for Searches:

    • Requirements under the 4th Amendment (search warrants needed unless there are exigent circumstances).

Sketching Techniques for Crime Scenes

  • Rough Sketches: Include measurements.

  • Final Sketches: Proportional representations maintaining necessary spatial relationships.

  • Methods for Measurement:

    • Triangulation and baseline measurements for accuracy.

Types of Physical Evidence

  • Almost anything can be considered as physical evidence.

  • Examples Include:

    • Objects: Tools, furniture, drugs, letters, etc.

    • Biological Materials: Blood, hair, tissues.

    • Impressions: Fingerprints, shoe prints, tool marks, etc.

Characteristics of Evidence

  • Class Characteristics: Shared by several items, often due to manufacturing similarities.

  • Individual Characteristics: Unique features that link evidence to a specific source.

  • Wear Characteristics: Alterations due to wear that may not individualize evidence.

Forensic Databases for Evidence Comparison

  • IAFIS: FBI National fingerprint database.

  • CODIS: Database for DNA profile comparison.

  • NIBIN: Firearm cartridge and bullet database.

  • National Integrated Ballistics Information Network: Links crime scenes via ballistic evidence.

The CSI Effect

  • Impact on Juror Expectations:

    • TV programs raise jurors' expectations for forensic evidence leading to some challenges in prosecutions.

  • Negative Impacts Include:

    • Higher demands for hard evidence, challenges finding impartial jurors, strains on forensic resources, and defense teams explaining evidence.

  • Positive Impacts Include:

    • Increased juror knowledge and public interest in forensic and criminal fields.

Death Investigation

Myths in Death Investigation (TV vs Reality)

  • Misconceptions include:

    • Quick determinations of time of death.

    • Ability to recreate the scene mentally.

    • All suicides leaving notes.

    • Medical Examiners determining cause of death conclusively every time.

Coroner System vs Medical Examiner System

  • Coroner: Quasi-judicial role; may not require formal medical training.

  • Medical Examiner (ME):

    • Requires a medical degree (M.D.) and specific training in pathology.

    • Complete fellowship and board certification, with extensive experience required.

Medicolegal Investigator (MLI) Requirements

  • Minimum qualifications include:

    • Degree related to Criminal Justice or Biological Sciences.

    • Three years of experience in relevant fields.

    • Skills in forensic investigation practices, documentation and proficient in terminology.

Cause & Manner of Death

  • Cause of Death: Medical determination based on evidence.

  • Manner of Death: Legal determination of circumstances surrounding the death;

    • Categories: Natural, Accidental, Homicide, Suicide, Undetermined.

Time of Death (TOD) Estimation Methods

  • Postmortem Interval (PMI): Time between last seen alive and found dead.

  • Methods Used Include:

    • Rigor Mortis (stiffness of muscles post-death).

    • Algor Mortis (changes in body temperature).

    • Livor Mortis (settling of blood post mortem).

Rigor Mortis

  • Classic marker that causes rigidity within 6 to 24 hours, with 12 hours being average.

    • Influenced by environmental factors such as temperature.

  • Considerations: Highly subjective and not completely reliable in estimations.

Algor Mortis

  • Refers to the cooling of the body post-mortem;

    • Must consider environmental conditions, clothing, body fat, and more to determine.

Livor Mortis

  • Blood settles to the lowest parts of the body due to gravity after the heart stops.

  • Maximum evident usually within 8-12 hours after death.

    • Indicates body position; patterns can give clues about positioning at death.

Stages of Human Decomposition

  • Stages:

    • Fresh (0-3 Days): Autolysis; bacteria move out of intestines internally.

    • Bloated (4-10 Days): Bacterial breakdown; gases build up.

    • Decay (10-20 Days): Corpse deflates; maggots consume flesh.

    • Post Decay (20-50 Days): Body reduced primarily to bones.

    • Dry Decay (50-365 Days): Only hair and bones remain.

Autopsy Process
Purpose:

  • To determine cause and manner of death through systematic examination.

Procedure Steps:

  1. Record circumstances of death prior to the autopsy.

  2. Document body characteristics (height, weight, identifying traits).

  3. Close examination of the body (clothing, skin).

  4. Check for signs of trauma, including dental records.

  5. Conduct thorough internal examination; check for any medical concerns.

  6. Record all findings and provide a report with cause of death.

Pressure and Asphyxiation

  • Force needed to asphyxiate based on anatomical regions:

    • Jugular Veins: 4-5 lbs

    • Carotid Arteries: 11 lbs

    • Trachea: 33 lbs

    • Vertebral Arteries: 66 lbs

Medical Terminology in Death Investigation

  • Anatomical Terms: Positions (anterior, posterior), body parts, relevant terminology.

  • Disease Terms: Common conditions, results of injury or trauma, etc.

Forensic Photography

Role of the Forensic Photographer

  • Produce objective, truthful images that represent the crime scene accurately.

  • Provide detailed images for scientific analysis and legal purposes.

Digital Imaging Practices

  • Preserve original images and document any enhancements done.

  • Enhancement vs. Alteration:

    • Enhancements are allowed but must be documented; alterations can misrepresent.

Techniques and Equipment for Forensic Photography

  • Important Photos:

    • Overview & itemized shots essential for evidence documentation.

  • Equipment Needed:

    • Cameras, various lenses, tripods, and photography scales for accurate evidence representation.

Lighting and Image File Formats

  • File Types: RAW (preferred) vs JPEG (compressed) for crime scene photography.

  • Lighting Techniques: Fill flash to illuminate dark areas; infrared photography for uncovering details.

Evidence Comparison in Photography

  • Importance of maintaining the integrity of photos; photo logs essential for court admissibility.

  • Special Lenses:

    • Macro lenses for close-ups; wide angle for scene overview.

Fire Investigation

Chemistry and Physics of Fire

  • Key Factors in Fire Investigation:

    • Proof of Incendiarism: Evidence of intention to burn.

    • Motive Identification: Includes financial gain, revenge, etc.

The Fire Tetrahedron

  • Fire requires heat, fuel, and oxygen; removing one element extinguishes the fire.

Types of Reactions in Fire

  • Oxidation: Combination of oxygen with other substances to create new products.

  • Heat of Combustion: Excess heat released during combustion.

Fire Behavior Analysis

  • Transfer of heat through conduction, convection, and radiation.

    • Conduction: Direct contact.

    • Convection: Movement of warm gases or liquids.

    • Radiation: Heat transmitted through space.

Important Definitions in Fire Science

  • Flashover: Instantaneous ignition of combustibles in a room.

  • Ignition Temperature: Minimum temperature to ignite a material.

  • Flash Point: Lowest temperature for enough vapor to combust.

Conducting Fire Investigations

  • Searching the Scene: Look for patterns of the fire spread and determining ignition sources.

  • Examples of Burn Patterns:

    • Alligatoring, low burning, smoke demarcation lines provide insights into the fire's origin and spread.

Collection and Analysis of Fire Evidence

  • Photograph evidence before collection.

  • Use appropriate containers for preservation.

  • Analyze residues with gas chromatography for accelerant detection.

  • Many signs indicating potential foul play or arson (e.g., multiple points of origin).

DNA Analysis in Forensic Science

Basic Components of DNA

  • Nitrogenous Bases: Adenine (A), Thymine (T), Cytosine (C), Guanine (G)

  • Forms the genetic code dictating biological traits.

Applications of Forensic DNA

  • Utilized in medical research, paternity tests, identification of missing persons, biological warfare detection, human evolution, and forensic science.

Short Tandem Repeats (STR)

  • Repeating sequences in DNA useful for individual identification based on DNA profiling.

Comparison of DNA Evidence

  • Types of DNA Used:

    • Nuclear DNA (nDNA)

    • Mitochondrial DNA (mtDNA)

Forensic Requirements for Effective DNA Evidence

  • Necessary samples for analysis, preservation of primers, and maintaining chain of custody for evidence.

High Sensitivity DNA Testing

  • Utilizes advanced methods to detect low copy number DNA, essential for degraded samples or low quantity evidence.

Fingerprints

Historical Aspects

  • Alphonse Bertillon: Introduced anthropometry for identification early in forensic history.

Characteristics of Fingerprints

  • Formed during fetal life; unique to each individual.

Fingerprint Types

  • Types of Prints:

    • Latent: Not visible until processed.

    • Visible: Easily seen by the naked eye.

    • Plastic: 3D impressions left in materials like wax.

Analysis Techniques

Collection Methods

  • Various techniques including powders, chemicals, and alternate light sources.

Standards in Fingerprint Comparison

  • AFIS (Automated Fingerprint Identification System) used for processing and matching prints.

Firearms Investigation

Core Aspects of Firearms Examination

  • Ability to match bullets and casings to specific firearms, determine the firing distance, and identify the weapon’s caliber.

Key Terminology in Firearms

  • Important Terms: Pistol, revolver, rifle, shotgun, caliber.

Identifying Bullet Characteristics

  • Examination of rifling patterns and striations on bullets can establish unique identifiers to a firearm.

Forensic Entomology

Role in Forensic Science

  • Assist in determining the time of death alongside toxicological analysis, indicating victim location and creating crime scene timelines.

Lifecycle of Flies in Decomposition

  • Insects such as blowflies play a crucial role in decomposition stages and can provide significant data regarding time since death based on their developmental stages.

Bloodstain Pattern Analysis

Importance of Blood Analysis

  • Investigates blood patterns to reveal clues about the origin, distance, direction, and force of impact related to the crime scene.

Types of Bloodstains

  • Categories Include:

    • Drop Patterns: Indicate fall direction and positioning.

    • Splash Patterns: Result from high-volume impacts.

    • Arterial Spurts: Indicate blood exit under arterial pressure.

Impression Evidence

Characteristics and Types

  • Evidence that retains characteristics from our environment, establishing connections to suspects or events (e.g., shoe prints, tire tracks).

Documentation Methods

  • Various techniques for documenting impressions, including sketches, photography, and use of lifting techniques for collection.