Comprehensive Overview of Forensic Disciplines and Practices

Organization and Structure of the FBI Laboratory

• The FBI laboratory is a massive operation consisting of more than $700$ employees.

• The laboratory is divided into $24$ distinct units, reflecting the diverse range of forensic disciplines required for modern investigations.

• Major disciplines within the laboratory include:

  • Chemistry.

  • Forensic Biology.

  • Digital Forensics.

  • Questioned Document Analysis.

  • Impression Evidence.

  • Firearms and Toolmarks.

  • Fingerprints.

  • Forensic Accounting.

Professional Requirements and Education in Forensic Science

• To become a competitive candidate in the forensic field, a double major is frequently required. This ensures a strong background in a core scientific discipline (e.g., Biology or Chemistry) in addition to specific forensic training.

• The forensic science degree itself typically comprises $30$ to $36$ credit hours, which essentially equates to one year of focused coursework.

• Upon graduation, students on this path receive two diplomas representing both the forensic science major and their additional scientific major.

• The necessity of a strong disciplinary background is critical for expert witness testimony. When testifying in court, professionals must establish their expertise not just in forensic procedures, but in the underlying scientific principles of their field (e.g., genetics for a DNA analyst).

• Specific background requirements for disciplines:

  • DNA Analysts: Must possess a deep understanding of biology and genetics to explain the "why" behind the analysis, not just the "how."

  • Forensic Chemists: Require a comprehensive mastery of basic chemistry to perform and explain chemical substance analysis accurately.

Forensic Chemistry and Toxicology

• Forensic Chemistry: This discipline focuses on the analysis of substances found outside the human body at a crime scene. A primary goal is the identification of unknown compounds.

  • Instrumentation: The primary tool used is the Gas Chromatographer-Mass Spectrometer ($GCMS$). Historical context: The FBI’s forensic chemistry room was known as the "$6,000,000$ room" because of the immense value of the many $GCMS$ units it contained; the current value is significantly higher due to technological advancement.

  • Substance Identification: Chemists determine if an unknown powder is a harmless substance (e.g., flour, powdered sugar, baby powder) or a controlled substance (e.g., cocaine, fentanyl).

• Toxicology: Often working within a medical examiner’s office, toxicologists focus on substances inside the human body.

  • They analyze biological samples for drugs, alcohol, and poisons.

  • Their role is to determine the concentration of these substances and assess if the levels were sufficient to cause death.

  • They also process samples from non-fatal incidents, such as blood draws from driving under the influence ($DUI$) stops.

Forensic Photography and Scene Documentation

• Forensic photography is not a standalone career path; it is an integrated, essential component of crime scene processing.

• It is considered the most important skill for a crime scene processor because high-quality photographs are the primary method for preserving evidence and showing the court (judge and jury) the original state of the scene, the body, and the evidence placement.

• Technical Skills Required:

  • Manual manipulation of camera settings to handle variable lighting conditions (e.g., extreme brightness or darkness).

  • Managing reflections when shooting through windows.

  • Capturing evidence that requires specific filters or light sources.

• Alternate Light Source (ALS): A specialized lighting tool used with filters to visualize evidence invisible to the naked eye through fluorescence.

  • Substances that fluoresce under ALS include semen, saliva, urine, sweat, and vaginal secretions.

  • Important Exclusion: Blood does not fluoresce.

Forensic Biology and DNA Analysis

• The Analysis Workflow:

  1. Visual Examination: Checking items (e.g., a jacket or knife) for biological material.

  2. ALS Examination: Using specialized light to find non-visible fluids.

  3. Documentation: Stains are circled and documented.

  4. Sampling: A small cutting or swab is taken for analysis. It is critical not to consume the entire sample so that further testing remains possible.

• Serology: This is the preliminary test used to determine what a substance is, whether it is human, and its relevance to the case. Serology is faster and cheaper than DNA analysis.

• DNA Profiling: The "gold standard" of forensic evidence.

  • Nuclear DNA: Found in the nucleus of the cell. It is unique to every individual with the exception of identical twins.

    • Identical Twins: Formed from one egg and one sperm that splits; they share the same DNA.

    • Fraternal Twins: Formed from two separate eggs and two separate sperm; they have different DNA.

  • Mitochondrial DNA (mtDNA): Found in the mitochondria. It is inherited exclusively from the mother (maternally inherited).

    • All siblings and maternal relatives (mother, maternal grandmother, maternal aunts/uncles) share the same mtDNA.

    • It is less definitive than nuclear DNA because it can only narrow a sample down to a family lineage, not a specific person.

    • It is used when nuclear DNA is degraded or missing, such as in old teeth, hair shafts, or bones without tissue.

• Advancements in Technology:

  • Extraction: The process of isolating DNA from cellular debris (ribosomes, mitochondria, etc.).

  • Automation: While a human can process a single extraction in $25$ to $30$ minutes, robotic systems can process $96$ samples simultaneously in less time.

• Historical Note: Nuclear DNA technology was validated in the U.S. around $1990$, and mitochondrial DNA around $1995$. Dr. Adams, a former FBI Laboratory director and former director of the Forensic Science Institute, was the first person to testify on DNA technology in a federal case.

CODIS (Combined DNA Index System)

• CODIS is the national DNA database for the United States, utilizing nuclear DNA profiles only.

• System Hierarchy:

  1. Local Level: Samples are run first against a local database (e.g., Oklahoma City) because crimes are often committed by repeat offenders in the same geographic area. This is a smaller, faster search.

  2. State Level: If no hit is found locally, the sample is sent to the state lab (e.g., OSBI). In Oklahoma, there are roughly $15,000$ profiles at the state level.

  3. National Level (NDIS): Samples meeting specific criteria (homicide, sexual assault) are uploaded to the federal level maintained by the FBI.

• Database Components:

  • Offender and Arrestee File: Includes all convicted felons and some misdemeanors. In "arrestee states" like Oklahoma, DNA is taken upon arrest, even if the person is not convicted.

  • Forensic File: Contains DNA profiles from unsolved crime scenes (e.g., tissue from under a victim’s fingernails).

  • Missing Persons File: Contains DNA from missing individuals or their relatives to help identify remains or persons with amnesia.

• Current Statistics (October 2024):

  • National level: Approximately $15,000,000$ offender profiles, $6,000,000$ arrestee profiles, and $1,300,000$ forensic profiles.

  • CODIS has assisted in over $709,000$ investigations and produced over $729,000$ hits.

  • Oklahoma specific: $193,000$ offender profiles, $14,000$ arrestees, and $12,000$ forensic samples.

Legal Implications and the Role of Forensic Scientists

• Guiding Principle: A forensic scientist’s duty is to speak to the value of the physical evidence and never beyond it. They do not work for the prosecution or defense; they work for the evidence.

• Wrongful Conviction and Exoneration: DNA is a powerful tool for proving innocence.

  • Exoneration: The act of proving a convicted person is innocent.

  • Kirk Bloodsworth: He was the first American sentenced to death to be exonerated by DNA. He spent nine years in prison for the rape and murder of a nine-year-old girl before DNA from a semen sample proved his innocence in $1993$. The actual murderer was identified in $2003$.

  • Earl Fuller Case: Fuller was convicted of raping two women based on eyewitness testimony and line-up identification. DNA evidence showed the semen from both crimes came from the same man, but that man was not Fuller.

• Eyewitness Testimony: Noted as one of the least reliable forms of evidence, particularly in cross-race identification.

• Innocence Project/Clinic: Students may work on backlogged cases of potential wrongful conviction. In Oklahoma, there is currently a backlog of approximately $500$ cases.

Trace and Impression Evidence

• Trace Evidence: Focuses on microscopic items like soil, glass, paint, and fibers.

• Hairs:

  • Hair analysis is no longer used for identification based on microscopic characteristics.

  • An FBI review found an $11\%$ error rate in cases where hair was used for identification before DNA was available.

  • Current use: Inclusion or exclusion (skin/hair color) and DNA source. Nuclear DNA can be found in the root, while mitochondrial DNA is found in the shaft.

• Impression Evidence: Includes shoe and tire tread patterns.

  • Class Characteristics: Features common to a group (e.g., every British Knight shoe or Converse All Star has a specific pattern). These can identify a type of shoe but not a specific individual shoe.

  • Individual Characteristics: Unique features like a cut in the tread, a chunk missing, or specific wear patterns. These can identify a specific item.

• Limitation of Impression Evidence: Identifying a shoe at a scene does not prove who was wearing it (e.g., a roommate could have borrowed it). Only DNA and fingerprints can directly identify a specific person.

Case Study: Flight 63 Shoe Bomber (December 2001)

• Suspect: Richard Reid.

• The Incident: Reid attempted to detonate an improvised explosive device ($IED$) hidden in his shoe while on a flight from Italy to Miami.

• Failure of Device: He attempted to light a match six times, but the bomb failed to ignite. Investigators believe his sweaty feet dampened the black powder, preventing combustion.

• Subsequent Analysis: After the crew and passengers subdued Reid and shifted the plane to Boston, the FBI conducted tests with pressurized planes to see the effect of such an explosion. This case is the reason passengers are required to remove shoes during $TSA$ screenings.

• Explosives Discipline: This forensic field typically requires a strong background in chemistry.