Exhaustive Forensic Science and Crime Scene Processing Guide

Firearms, Tool Marks, and Impression Evidence

  • Ballistics Testing and Bullet Markings:

    • When evaluating a firearm suspect's weapon, test bullets are fired directly into a specialized water tank.
    • Water decelerates the projectile smoothly, preserving delicate microscopic markings on the bone or metal of the bullet without introducing external defects, impact distortions, or wall-contact scrape marks that occur when shooting into solid barriers.
    • The interior barrel of every firearm leaves unique microscopic striations and markings on fired bullets and cartridge cases during discharge.
    • Forensic examiners use a comparison microscope (or dual digital view screens) to inspect crime scene bullets and test-fired bullets simultaneously, evaluating whether unique striations match in precise shape, spacing, and spatial location.
    • Matching bullet markings proves that a bullet was discharged from a specific individual gun; it does not directly identify the individual person who fired the weapon. For example, a suspect's roommate could take the firearm and commit a crime without the owner's knowledge.

  • Direct Person-Identification Evidence:

    • Only two types of forensic evidence directly link a crime to a specific individual person:
      1. Fingerprints
      2. DNA
    • All physical impression evidence (such as firearms, tool marks, footwear impressions, and tire tracks) identifies an object, not a person. Supplementary evidence is mandatory to establish who was wearing the shoe or holding the weapon during the offense.

  • Tool Mark Examination:

    • Firearms examiners are simultaneously qualified as tool mark examiners.
    • When tools (e.g., hammers, pliers, crowbars) are used to force entry into a structure, they leave microscopic tool mark impressions on the surface.
    • Examiners obtain search warrants for a suspect's toolbox and create control test impressions using the seized tools.
    • Examiners compare crime scene impressions to test impressions under microscopic magnification to identify unique manufacturing imperfections and wear characteristics specific to that single tool.

  • Footwear and Impression Evidence:

    • Impression evidence encompasses shoe tracks, tire impressions, and tool indentations left at crime scenes.
    • Class Characteristics:
      • General design parameters introduced during manufacturing that exist on every production unit of a specific brand, style, and size.
      • Examples include the brand name (e.g., British Knight, Converse, Reebok), circular tread designs, specific heel geometry, or distinct chevron tread patterns.
      • Class characteristics narrow down the brand, tread type, and size of the shoe, but cannot isolate a single specific shoe.
    • Unique / Individual Characteristics:
      • Specific acquired defects or wear patterns unique to a single item.
      • Examples include specific tread wear locations (e.g., wearing down the inner heel versus the lateral outsole edge), cuts, gouges, missing chunks of rubber, or gravel embedded in the tread.
    • Recovery and Processing Methods:
      • Three-dimensional impressions left in soft substrates like sand or soil are recovered by casting the impression with dental stone.
      • Footwear image databases allow investigators to upload crime scene tread images to quickly search and identify the exact shoe brand and model pattern.

  • Dramatization Case Analysis (Heel Impression Case):

    • In a case scenario involving three unidentified heel prints with a distinct chevron pattern (identified as Group 33 20002000 pattern), the heel provided only class characteristics, belonging to multiple shoe models of that design line.
    • Soil trapped inside the heel treads provided critical trace evidence to supplement the non-definitive class impression data.

Crime Scene Processing and Fieldwork

  • Soil Dynamics in Trace Evidence:

    • Soil recovered from footwear, tires, or clothing is submitted to the trace evidence unit.
    • Trace analysts evaluate physical composition, elemental constituents, and chemical characteristics (including pH levels).
    • Soil composition varies significantly across localized geographic zones; for example, soil composition and pH in West Edmond differ markedly from soil in East Edmond.

  • Aviation Security Context:

    • Mandatory shoe removal at TSA security checkpoints stems from historical terrorist incidents, such as Richard Reid attempting to detonate an improvised explosive device (IED) hidden inside his footwear aboard a pressurized commercial airliner.

  • Crime Scene Processing Procedures & Team Roles:

    • Evidence Response Team (ERT): Specialized FBI crime scene operational units equipped to process complex crime scenes and conduct mass grave excavations.
    • Standard crime scene processing involves 1212 systematic steps executed across 66 specialized team positions.
    • Sequential processing tasks include:
      1. Scene photography.
      2. Writing detailed written narrative descriptions of all observations.
      3. Crime scene sketching.
      4. Evidence identification.
      5. Evidence collection.
      6. Packaging evidence securely.
    • Importance of Collection: Laboratory analysts cannot test evidence that field processors fail to recognize and collect. Investigators must exercise critical judgment to distinguish probative evidence from background clutter (e.g., processing severe hoarding environments).
    • Occupational Realities and Biological Hazards:
      • Field investigators face direct exposure to biological materials, including blood, semen, saliva, decomposing tissues, loose human hair, and body secretions.
      • Midwest City Crime Lab Incident (Investigators Megan Radix and Keisha Jones): While executing a search warrant at the residence of a suspect accused of inappropriate behavior with teenage girls, investigators encountered severe unsanitary conditions, including jars containing urine, stored human hair, jarred toenail clippings, unwashed inside-out stained underwear, and a used tampon left on a bedside table with a cockroach crawling across it.
      • Edmond Suicide Investigation: An explosive suicide scene where an individual poured gasoline over himself, placed his head on or in a stove, and ignited an explosion, demonstrating the graphic nature of field responses.

  • Lost Property Protocols:

    • Recovered personal items (e.g., cell phones, AirPods) at facility locations are submitted to front desk administration (Roberta) for secure inventory logging.

Death Investigation, Advanced Technologies, and Forensic Entomology

  • Death Scene Investigation versus Local Crime Scene Processing:

    • Local Crime Scene Unit (e.g., Edmond Crime Scene Unit): Processes the surrounding physical scene, physical objects, impression evidence, and spatial layout.
    • Medical Examiner / Death Scene Investigator: Holds sole responsibility for the deceased body. They assess postmortem changes, estimate the postmortem interval (time interval of death), collect body evidence, and manage transport to the morgue for autopsy by a forensic pathologist. Unattended deaths trigger death scene protocol.
    • Forensic Anthropologist: Called to analyze skeletal remains, bone fragments, and heavily decomposed human remains.

  • Personal Protective Equipment (PPE) & Scene Integrity:

    • Investigators wear full Hazmat suits, double gloves taped securely at the sleeves, and footwear covers.
    • Dual Purpose of PPE:
      1. Protects investigators from biohazards and bloodborne pathogens.
      2. Protects the crime scene from investigator-induced contamination (eliminates stray fingerprints, shed hairs, footwear impressions, or external DNA).

  • Advanced Scene Mapping:

    • Faro Technology: Uses 3D3\text{D} laser imaging scanners to generate complete three-dimensional digital reconstructions of physical crime scenes for virtual mapping and computer analysis.

  • Mass Graves and Disaster Victim Identification (Kosovo Case Study):

    • Kosovo (19991999): Mass graves resulted from political militia violence and genocide.
    • The FBI Evidence Response Team deployed specialized tools to carefully excavate human remains without fracturing skeletal elements.
    • Identification Challenges: Lack of national DNA databases, absence of reference DNA samples, and lack of dental records due to rural healthcare limits.
    • Resolution Method: Victims were successfully identified by calling in surviving family members to examine personal items, clothing remnants, and jewelry recovered directly alongside the remains.

  • Forensic Entomology:

    • Analyzes insect life cycles and colonization sequence on decomposing bodies to determine the time interval of death (postmortem interval, PMI), rather than an exact, pinpoint time of death.
    • Sequential Colonization Cycle:
      1. Blowflies: Arrive within minutes to hours, attracted by blood and decay odor. They lay eggs in body orifices (eyes, ears, nose, mouth, anus) and traumatic wounds (stab or gunshot wounds).
      2. Eggs to Larvae (Maggots): Eggs hatch into feeding larvae.
      3. Pupation to Adult Flies: Larvae mature into blowflies.
      4. Carrion Beetles: Arrive in subsequent stages as decomposition progresses.
    • Environmental Variables: Ambient temperature, humidity, indoor versus outdoor exposure, and wildlife interference alter colonization rates.
    • Entomological Toxicology: In skeletonized or heavily decomposed remains where human soft tissue is absent, insects feeding on the remains are harvested and analyzed chemically to detect drugs, poisons, or toxins present in the victim's body at death.

Forensic Media Realities and Microbial Forensics

  • Analysis of Crime Scene TV Tropes vs. Field Realities:

    • Flaws and Inaccuracies Identified in TV Portrayals:
      • Handling or manipulating a body prior to verifying vital signs or completing mandatory photography and sketching.
      • Failure of first responders to verify a pulse immediately.
      • Absence of PPE: Investigators wearing high-fashion attire (e.g., white trousers) with loose, untied hair dangling near biological evidence.
      • Lack of scene security: Omission of crime scene perimeter tape and failure to maintain a mandatory Crime Scene Control Log (entry/exit tracking register).
      • Grossly exaggerated maggot volumes (e.g., bowls full of maggots or hundreds dropping through ceiling spaces).
      • Conducting investigations in dark environments using hand-held flashlights for dramatic ambience rather than establishing full lighting to ensure complete evidence recovery.
    • Accurate/Realistic Portrayals in TV Media:
      • Estimating time intervals of death via insect developmental stages.
      • Medical examiners measuring liver temperature (algor mortis) on-scene to assess postmortem cooling.
      • Maggot Debridement Principle: Maggot larvae feed exclusively on necrotic (dead) tissue, leaving healthy tissue intact and consuming bacteria, which can slow bacterial infection spread.
    • Forensic Media Evaluation:
      • Dramatic/Fictional: Dexter (bloodstain pattern analysis within a serial killer plot), CSI, Criminal Minds.
      • Accurate/Documentary-Style: Forensic Files, The First 48, 60 Minutes (featuring real forensic scientists, authentic evidence, and actual casework).

  • Microbial Forensics:

    • Field combining microbiology, genomics, and DNA profiling to analyze biological pathogens, viral agents, and bacteria for legal and national security investigations.
    • Amerithrax / 20012001 Anthrax Mailings Case Study:
      • Occurred in 20012001 following the September 1111 terrorist attacks.
      • Lethal anthrax spores were sent via U.S. mail to high-profile news anchors and U.S. Senators.
      • 55 fatal victims were non-targeted individuals (postal workers and recipients) who opened or processed contaminated mail.
      • Investigators used advanced genomic sequencing to trace the specific genetic strain of anthrax back to a specific research laboratory, identifying the manufacturer.
      • Safety Precautions: Microbial forensic processing requires specialized biosafety containment hoods and full isolation gear to prevent fatal exposure.

  • Behavioral Analysis Unit (BAU):

    • Focuses on offender behavioral profiling, trophy taking, serial offenses, overkill, and psychological analysis.
    • Career Requirements:
      • Must qualify and serve as an FBI Special Agent.
      • Requires a minimum of 77 years of active service investigating violent crime cases prior to recruitment into the BAU.

Forensic Science Definitions, Laboratory Disciplines, and Student Organizations

  • Student Academy of Forensic Sciences (SAFS / SAS):

    • Campus Forensic Science Club meeting bi-weekly on Wednesdays from 12:00proposal PM12:00 proposal\text{ PM} (12:00 PM12:00\text{ PM} to 1:00 PM1:00\text{ PM}); initial informational meeting on September 99.
    • Dues: 10 USD10\text{ USD} per semester or 15 USD15\text{ USD} per academic year. Open to all student majors.
    • Activities: Guest lectures (FBI, OSBI, evidence technicians), community outreach (STEM camp Project Science at the National Memorial Museum, Big Brothers Big Sisters programs, elementary school workshops), escape rooms, and seasonal events.
    • Affiliated Student Organizations: Delta Delta Epsilon (Forensic Honor Society) and Cold Case Club (investigates unsolved cold cases).

  • Definition and Terminology of Forensic Science:

    • Core Definition: The application of science to law.
    • Alternative Formulations: The application of science to criminal and civil laws; or science associating people, places, and things involved in criminal activities.
    • Synonymy: Criminalistics is synonymous with forensic science; a job posting for a "criminalist" is a forensic science position.

  • Forensic Application to Counter-Terrorism and War:

    • Forensic methodology extends beyond municipal law into military and intelligence operations (the application of science to war).
    • Iraq IED Suicide Bombing Case: Following a suicidal IED bombing that killed U.S. service members in Iraq, forensic technicians recovered a latent fingerprint from an IED component, matching it to a bomb maker registered in a detention database.
    • TEDAC (Terrorist Explosive Device Analytics Center): A centralized intelligence database utilized to analyze explosive components, device construction, and terrorist organization signature profiles.

  • Full-Service Forensic Science Laboratory Units:

    1. Biology Unit: Handles serological screening and DNA analysis.
    2. Trace Evidence Unit: Employs microscopic analysis to examine micro-particles such as glass, paint chips, soil, hair, and synthetic/natural fibers.
    3. Chemistry Unit: Analyzes controlled substances/illicit drugs, explosives, pressure-sensitive tapes, toxins, and poisons.
    4. Impression Evidence Unit: Evaluates footwear impressions, tire tracks, questioned documents, tool marks, and firearms (fingerprints and firearms frequently operate as standalone specialized units).
    5. Digital Evidence Unit: Performs forensic extraction and examination of computers, mobile phones, and digital storage media.
    • Full-Service Facilities in Oklahoma: Oklahoma State Bureau of Investigation (OSBI), Oklahoma City Police Department (OCPD), and Tulsa Police Department (TPD). Partial service facilities include Edmond PD and Midwest City PD.
    • Market Trends: DNA analysis and Digital Forensics represent the most financially viable and rapidly growing sectors, offering extensive employment in both public law enforcement and private enterprise (e.g., private DNA laboratories, Paycom).

External Forensic Specialists and Historical Foundations of Identification

  • External Forensic Specialists:

    • Crime scene team leaders must identify when specialized external consultants are required beyond standard lab personnel:
      • Forensic Pathologist / Medical Examiner: Autopsy and cause/manner of death.
      • Forensic Entomologist: Insect development and postmortem interval estimation.
      • Forensic Odontologist: Human identification through dental record comparison. Note on Bite Mark Analysis: Bite mark comparison is scientifically discredited and being phased out due to skin elasticity distorting bite mark geometry, causing high error rates in distinguishing human, animal, adult, or child bite marks.
      • Forensic Anthropologist: Analysis of bony structures and skeletal remains.
      • Forensic Engineer: Evaluation of structural failures, building collapses, bridge failures, and mechanical disasters.
      • Wildlife Forensic Scientist: Investigation of crimes involving protected or endangered wildlife species.
      • Weapons of Mass Destruction (WMD) Specialists: Response to Chemical, Biological, Radiological, or Nuclear (CBRN) incidents.

  • History of Identification Systems:

    • Alphonse Bertillon and Anthropometry:
      • In 18791879, Alphonse Bertillon of the Paris Police Department created Anthropometry (Bertillonage).
      • Based on taking 2222 precise physical body measurements (e.g., eye spacing, arm length, ear dimensions, head circumference).
      • Premise: Premised on the belief that no two human beings possess identical combinations of all 2222 body measurements.
    • The Will West and William West Case:
      • In the early 1900s1900\text{s} at Leavenworth Penitentiary in Kansas, two incoming inmates named Will West and William West were found to possess virtually identical facial features and identical sets of 2222 Bertillon anthropometric measurements, despite being distinct individuals (later believed to be separated identical twins).
      • This critical failure exposed the unreliability of anthropometry, forcing law enforcement globally to abandon Bertillonage in favor of fingerprint identification.
    • Historical Origins of Fingerprinting:
      • Historical records demonstrate that Chinese authorities recognized that fingerprints could uniquely identify individual persons as early as 792 AD792\text{ AD}.