Fingerprint Analysis, Forensic Genealogy, and Legal Standards

Posted on Jan 12, 2025 in Criminological and Security Sciences

Fingerprint Patterns and Analysis

Level 1 Patterns

  • Arch
  • Tented Arch
  • Right Loop (delta on left)
  • Left Loop (delta on right)
  • Plain Whorl (two deltas, horizontal)
  • Central Pocket Loop (two deltas)
  • Double Loop (two deltas)
  • Accidental Whorl

Level 2: Minutiae

Ridges that make fingerprints unique:

  • Dot
  • Bifurcation
  • Lake
  • Ridge ending
  • Bridge
  • Hook

Level 3 Details

  • Wrinkle: Identify individual ridges; these are raised portions called friction ridges, and the spaces between the ridges are called furrows.
  • Scar: Result from injury that damages the dermal layer where the ridges of fingerprints form; when a scar heals, it can alter the pattern of ridges.
  • Pore: Tiny duct at the opening on the ridges of fingerprints (associated with sweat glands).
  • Wart: Interfere with daily activities, cause discomfort, and alter the appearance of nails/fingerprints.

Fingerprint Visualization and Collection

Visualization Techniques

  • Powders: Adhere to moisture/oil left behind, making them visible against surfaces.
  • Small Particle Reagent (SPR): Suspends fine particles in a solution that adheres to the oily component of fingerprints, creating contrast against the surface (useful on porous/rough surfaces).
  • Physical Developer: A chemical method to visualize prints by depositing a silver/gold substance on the residue of the print.
  • Super Glue Fuming (SGF): Heat cyanoacrylate; it reacts with amino acids, creating a white residue that is visible.
  • Fluorescence Identification: Fluorescence dyes that adhere to compounds in fingerprint residues, making them glow under specific wavelengths of light.

Collection Methods

  • Photography: A visual record.
  • Scanning: Digital representation in a secure database, used for identification and verification purposes.
  • Lifting: Preserve/collect evidence from a surface (proper handling/storage to prevent contamination/breakage).
  • Casting: A 3D impression using dental stone or dental plaster.

Fingerprint Matching and Systems

  • Fingerprint Matching: Using automated systems that analyze unique patterns/minutiae points present in the ridges/valleys of a print; compare a known print (database) to an unknown print (crime scene).
  • Automated Fingerprint Identification System (AFIS): Preserves fingerprints by scanning/digitalizing them, creating a unique digital representation of the ridges/patterns.
  • Analysis, Comparison, Evaluation, Verification (ACE-V): A scientific method for the examination and documentation of fingerprints.
  • Collection of Exemplars: Fingerprints deliberately collected from a suspect.

Impression Evidence

Associate points in the Evidence Linkage Triangle (Scene, Subject, Victim).

High-Quality Photography

(a) Scales: Ensure the size/proportions of objects stay constant so they can be accurately assessed later; maintain the integrity of the evidence/facilitate accurate analysis.

(b) Lighting: Capture accurately and without distortion.

Specific Types of Impression Evidence

  • Snow: Adding something for background will help.
  • Sand: Better when wet; spray with a contrasting color after the first shot.
  • Tire Tracks: Overall photo first; mid-range with each segment labeled; close-ups of overlapping 12-18” segments.
  • Bite Marks: Shallow but 3D; the angle of light is more critical; flash stays on; mid-range shots to establish the location of bites.
  • Indented Writing: Angles of slash very low and diagonal.
  • Dust Prints: Positive dust is on an object and is left on a clean surface; Negative dust is on a surface, and an object coming into contact lifts it away.
  • Tool Marks: Must show details of the mark.

Casting Materials

  • Rubber Casting: For tool marks on nearly all surfaces; silicone material captures microscopic details.
  • Mikrosil: Silicone-based casting material; best for hard surfaces; tool marks/fingerprints; not for bite marks on skin; captures fine detail better than silicone putty.
  • Dental Stone: On 3D impressions; always photograph before; mixed on-scene, then poured on the impression; once dry, the cast is recovered.
  • Gelatin (2D): Gel lifter, an adhesive lifter applied like fingerprint lifting tape; clear covers are applied over the lift after recovery.
  • Adhesive Lifter (2D): Adhesive-coated material/tapes to lift impressions.

Firearm Analysis

Firearm Functionality Testing

  1. Bullet removed from the cartridge.
  2. Toilet paper is loosely stuffed into the cartridge case.
  3. The cartridge case is loaded into the firearm.
  4. The firearm is fired into a receptacle, such as a tissue-filled sharps container.
  5. The receptacle is checked for a fired projectile.

Firearm Impressions

  • Firing pin
  • Breech face marks
  • Rifling striations
  • Extractor marks
  • Ejector marks

Gunpowder Analysis

Performed by firearm examiners, it incorporates test fires at multiple distances using the same firearms/ammunition type; the pattern will change with distance before disappearing.

Genealogy in Forensic Science

  • Genealogy: The study of families (historical records) to determine relationships/family trees.
  • Genetic Genealogy: Genetic data and traditional genealogy to determine the level and type of relationships between people; adoptees’ parents.
  • Forensic Genetic Genealogy: Genetic genealogy in a legal context to identify Jane Does and perpetrators of violent crimes.
  • Forensic Genealogy: The study of identity and kinship in legal contexts (heirs).
  • CentiMorgan (cM): A unit of genetic measurement; experts use it to describe how much DNA you share with someone.
  • CentiMorgans Passed Down: A child receives 50% from each parent; different children receive different pieces.

Information to Solve Genetic Genealogy Cases

Crime scene evidence, genealogical databases, public records, online genealogy platforms, law enforcement databases, DNA databases, social media, the internet, and forensic reports.

Steps to Process Genetic Genealogy Cases

  1. Evaluate the case.
  2. Determine who you are trying to find.
  3. Identify matches.
  4. Build back.
  5. Identify Most Recent Common Ancestors (MRCAs).
  6. Build forward.
  7. Connect trees.
  8. Identify candidates.
  9. Confirm cMs.
  10. Give tips to law enforcement.

Narcotics and Controlled Substances

  • Narcotic: Part of the opioid system that controls pain, pleasure, and addictive behaviors.
  • Opiate: Derived from the milky-white secretion of the poppy plant, Papaver somniferum (e.g., morphine, codeine).
  • Opioid: A broad term that refers to drugs synthesized from opiates; narcotic analgesics manufactured by synthesis, not involving constituents of opium (e.g., heroin).
  • Central Nervous System (CNS) Stimulants: Cause excitement, loss of fatigue, decreased appetite, and increased wakefulness.
    • Amphetamine: Similar to cocaine; taken orally or ingested (stimulant drug).
  • Hallucinogens: Effects like psychosis; altered perceptions of visual, auditory, and tactile stimuli.
  • Cannabinoids: (e.g., THC) Chemical components in cannabis (the plant itself); active compounds that interact with the body’s endocannabinoid system, influencing physiological processes.
  • CNS Depressants: Depress the activity of the CNS, causing sedation and hypnosis.
  • Anabolic Steroids: Synthetic variations of testosterone used to promote/enhance muscle growth/appearance.
  • Adulterants: Drugs added to mimic/enhance the effects of an illicit drug.
  • Diluent: Compounds like sugars used to increase the bulk of a drug sample.
  • Impurity: Drug compounds like noscapine that are present in opium/coca leaves and carried over during the drug production process.
  • Field Tests: Presumptive tests in which small samples of a suspected controlled substance are tested with a single chemical reagent or a series of these; colors produced in the reaction can indicate a particular drug.

Forensic and Clinical Psychology

Forensic Psychology

Treatment of incarcerated individuals; treatment for committed individuals; treatment to restore competency.

Clinical Psychology

Mandated reports/duty to warn; requesting emergency evaluations; testifying as a fact witness; educating authorities on roles/limitations.

Roles of Psychology in the System

Evaluation in child protection matters; evaluation for child custody in divorce; civil commitment determination; protecting client rights; profiling criminals.

Legal Standards and Expert Testimony

Frye v. United States: It set a precedent for the admissibility of scientific evidence in court. It established the “Frye standard,” stating that scientific evidence must be generally accepted by the relevant scientific community to be admissible in court, emphasizing the importance of consensus within the scientific community for the admissibility of expert testimony of evidence.

Daubert Standard or Federal Rules of Evidence 702: A rule used in U.S. federal courts to assess the admissibility of expert witness testimony. Federal Rule of Evidence 702 governs this standard, requiring that expert testimony be based on reliable scientific knowledge, relevant to the case, and presented by qualified experts to assist the trier of fact. This standard aims to ensure that expert testimony is grounded in valid methodology and can withstand scrutiny before being admitted as evidence in court.

Qualified Expert: In court, a person can be qualified as an expert if they possess specialized knowledge, skill, experience, training, or education in a particular field that goes beyond what an average person would have. The judge determines whether someone qualifies as an expert based on their credentials and the relevance of their expertise to the case. The key is that the person’s expertise must directly relate to the subject matter of the case, and they should be able to assist the judge or jury in understanding complex technical or specialized information relevant to the case at hand.

Crawford Case: It ruled that testimonial standards made by unavailable witnesses, which are admitted as evidence without the opportunity for the defendant to cross-examine, violate the defendant’s constitutional right to confront witnesses against them. This decision narrowed the admissibility of certain types of hearsay evidence, particularly testimonial statements, in criminal trials, requiring a declarant to be available for cross-examination unless an exception applies.

Pre-Trial: A phase in a legal case that occurs before the actual trial. It involves various procedures, discussions, and preparations by both the prosecution and defense, often overseen by a judge. During this phase, parties may engage in motions, evidence discovery, plea bargaining, and other pre-trial proceedings aimed at clarifying issues, narrowing down points of contention, and potentially reaching settlements. It’s a crucial stage where the groundwork for the trial itself is laid, streamlining the actual proceedings and potentially leading to resolutions without a full trial.

Steps of Expert Testimony

  1. Direct Qualification: Requires the witness to possess specialized knowledge, skills, education, or experience relevant to the case; the expert must demonstrate their qualifications, expertise, and the relevance of their testimony to assist the judge or jury in understanding complex issues central to the case.
    1. Cross: Typically requires qualifications similar to those of the initial expert witness; the expert offering cross-testimony should possess specialized knowledge, education, experience, or training relevant to the subject matter and be capable of addressing or challenging the assertions made by the opposing party’s expert witness. They should also meet the standards set by the court for expert testimony admissibility under rules such as Federal Rule of Evidence 702 or other relevant legal guidelines.
  2. Direct Interview: Involves the attorney or legal team directly questioning the expert witness they’ve called to testify. It aims to elicit information supporting the case, allowing the expert to explain their qualifications, analysis, and conclusions regarding the subject matter, helping to educate the judge or jury and strengthen the case presented.
  3. Cross-Examination: Involves questioning the expert witness by the opposing party to challenge their qualifications, methods, conclusions, and credibility. The goal is to undermine the expert’s opinions, expose potential biases or flaws in their analysis, and create doubt in the minds of the judge or jury regarding the reliability of the expert’s testimony.
  4. Re-Direct: A trial occurs after the cross-examination of a witness, allowing the attorney who initially called the witness to clarify or rehabilitate any points that might have been challenged or confused during cross-examination. It aims to reinforce the witness’s credibility and the point favorable to their testimony, offering explanations for any issues raised during cross-examination.