Fingerprint Evidence

Chapter 6: Fingerprint Evidence

Instructor: O'Neil

Topic: Crime Scene/Forensic Science Technology

Objectives

  • Identify key concepts related to fingerprint evidence.

  • Discuss fingerprints and palm prints.

  • Identify where to look for fingerprints at crime scenes.

  • Differentiate between types of fingerprints.

  • Explain developing techniques for identifying fingerprints.

  • Outline preservation techniques for evidence.

  • Mention other types of prints and their relevance.

  • Explore elimination fingerprints and their importance in investigations.

  • Discuss decedent fingerprints and protocols for collection.

  • Introduce Adobe Photoshop for image enhancement.

  • Overview of IAFIS & NGI systems for fingerprint identification.

Identity

  • Crucial Aspect in Solving Cases:

    • Fingerprints serve as an essential method for identification in forensic investigations.

    • Other identification methods include:

      • Forensic anthropology

      • Forensic odontology

      • DNA analysis

      • Facial recognition technology.

Fingerprints and Palm Prints

  • Most Valuable Clues:

    • Fingerprints and palm prints provide critical evidence at a crime scene.

    • Footprints can also serve as known exemplars for comparison.

  • Characteristics of Fingerprints:

    • Composed of friction ridge skin present on palms, fingers, and soles of feet.

    • Three Basic Principles:

      • Individual characteristics unique to each person.

      • Remain unchanged throughout a person’s lifetime.

      • Ridge patterns can be systematically classified for easier analysis.

Where to Look for Fingerprints

  • Potential Locations for fingerprint collection:

    • Entry and exit points, e.g., doors, locks, and surrounding areas.

    • Areas with broken glass, windowsills, and door jambs.

    • Locations where food or drinks have been consumed (drinking or eating).

    • Surfaces such as light switches, light bulbs, circuit breakers, doorknobs, and drawers.

    • Tools and items like flashlights and batteries.

    • Toilets, inside latex gloves, smooth surfaces (glass), and paper.

    • Utilization of oblique lighting for better visibility of prints.

Types of Fingerprints

  • Major Types:

    • Plastic Fingerprints:

    • Formed when fingers touch or press against a material, creating an indentation (negative impression).

    • Characteristics:

      • Visible, requiring no enhancement.

      • Commonly located on fresh paint, adhesive tape, soap, wax, chocolate.

    • Patent Fingerprints:

    • Result from fingers that have foreign substances on them, which contact another surface.

    • Characteristics:

      • Visible without enhancement.

      • Substances can include ink, soot, flour, make-up, oils, or blood.

    • Latent Fingerprints:

    • Composed of a small amount of grease, sweat, and dirt; difficult to detect with the naked eye.

    • Characteristics:

      • Secretions are approximately 98.5 – 99.5% water.

      • Not visible without processing; require specific developing techniques for visibility.

Developing Techniques

  • Importance:

    • Knowledge of various techniques is crucial for effective fingerprint development; order of procedures matters.

  • Cautions:

    • Some methods may have negative effects (e.g., ink running or destroying DNA).

    • Implement safeguards to prevent destruction of physical evidence.

Development with Powders

  • Process:

    • Brushing powder over a latent print can make it visible.

    • Considerations:

    • Select powder based on the surface and type of fingerprint.

    • Common powder types:

      • Black, white, colored, aluminum, copper, fluorescent, and magnetic.

      • Choose based on background color and surface nature.

  • Brush Types:

    • Fiberglass, animal hair, synthetic, and natural brushes.

    • Care must be taken to avoid contaminating prints with damp or oily substances.

    • Technique:

    • Lightly dip brush in powder, tap off excess - small amounts are effective.

    • Use circular motions; avoid sprinkling or excessive powder.

    • Magnetic Applicators:

    • Used to apply powder and remove excess without damaging prints.

    • Safety:

    • Refer to Safety Data Sheets (SDSs); long-term exposure to powders can lead to respiratory issues.

Types of Processing - Powders

  • Black Fingerprint Powder:

    • Universal developer for smooth nonporous surfaces.

  • Magnetic Powder:

    • Uses streamers of magnetic powder that adhere to latent prints and facilitate cleaning excess.

  • Fluorescent Powder:

    • Applied under UV light for visibility in special circumstances.

Other Processing Techniques

  • Iodine:

    • One of the oldest methods, effective on both porous and nonporous items.

    • Vapors produced are toxic and corrosive; not a permanent solution.

  • Ninhydrin Solution:

    • Designed for porous surfaces; reacts with amino acids producing purple color.

    • Increased effectiveness in warm, humid conditions.

  • Physical Developer (PD):

    • Silver-based solution ideal for porous surfaces that were wet, yielding gray or black prints.

  • Silver Nitrate:

    • Reacts with chlorides but is not widely used due to the presence of PD.

  • Amido Black:

    • Stains proteins in blood blue-black, often used in conjunction with other techniques.

  • DFO (1,8-diazafluoren-9-one):

    • Reacts with proteins to create highly fluorescent red prints.

  • Gentian Violet or Crystal Violet:

    • Reacts with fatty components; produces a purple color applicable to adhesive tapes.

  • Small Particle Reagent (SPR):

    • Used on nonporous, wet surfaces; reacts with lipids to produce gray prints.

  • Sudan Black:

    • Effective on nonporous surfaces; used for oily or greasy prints, yielding blue-black results.

  • Cyanoacrylate Fuming (Superglue):

    • Utilized on nonporous surfaces to produce white prints, which can subsequently be dusted or washed with dyes.

  • Vacuum Metal Deposition (VMD):

    • Involves using gold and zinc in a vacuum chamber for high-definition results, applicable for DNA swabbing; however, it's expensive and has size constraints.

Laser and Alternative Light Sources

  • Laser Technology:

    • Effective for locating latent prints and other biological evidence through light amplification by stimulated emission of radiation.

    • Not all processes utilize a single wavelength; some lasers are portable while others require significant setup.

    • Caution:

    • Risks of eye fatigue and damage necessitate eye protection during use.

  • Reflective Ultra Violet Imaging Systems (RUVIS):

    • Utilized for latent prints that fluoresce under specific lighting conditions.

Preservation Techniques

  • Photography:

    • Essential in preserving fingerprint location evidence for courtroom presentations; may require specialized techniques.

    • Importance of achieving accurate and true photographic scale (1:1 ratio) is emphasized for reliability.

  • Plastic Fingerprints:

    • Can be hardened and stabilized for transport; photograph using oblique lighting conditions.

  • Casting Material:

    • Gel lifters utilized for fingerprints or footprints; thin, adhesive, and often mirror images.

  • Lifting Techniques:

    • Fingerprint-lift tape used to collect prints; tape is dusted, placed over the fingerprint, lifted, and adhered to a card.

    • Insufficient ridge detail may require DNA backing.

Fingerprints Remain on Object

  • Variables Impacting Print Longevity:

    • Secretion components, pressure applied, environmental conditions, and nature of the item all play significant roles.

    • Contaminated prints (e.g., soot, flour) are not durable; however, blood, ink, and oil tend to resist degradation under suitable conditions.

    • Smooth objects like glass can preserve prints for years if adequately protected, while prints on paper are stable for numerous years unless exposed to moisture or deterioration.

Effects of Temperature Conditions

  • Cold Environments:

    • Slow heating of residences may necessitate scraping away snow or ice to access fingerprints.

    • Oils and grease prints must thaw carefully to avoid destruction due to heat exposure.

    • Dew and moisture on surfaces call for drying indoors, ensuring room temperature maintenance for best results.

Examination of Developed Fingerprints

  • Search and Preservation:

    • Search for, develop, and preserve small or fragmentary prints which may bear evidentiary value; larger prints do not guarantee higher value.

  • Expert Insight:

    • Examination requires vast expertise and specialization in fingerprint identification.

Other Types of Prints

  • Palm Prints

    • Exhibit similar evidentiary value as fingerprints; currently over 15 million entries in the National Palm Print System (NPPS).

  • Footprints

    • Evidence from soles of feet is valuable and shares comparisons similar to fingerprints.

  • Ear and Lip Prints

    • Utilized in forensic investigations:

    • Ear prints measure auricle morphometry.

    • Lip prints (cheiloscopy) can be retrieved from items like letters or cups and require direct comparisons with exemplars.

  • Glove Prints

    • Can provide valuable evidence – often needing comparison against the gloves involved.

  • Human Skin

    • Printing from skin remains limited, but under specific conditions can be valuable; pressing Kromekote cards against skin for three seconds can reveal valuable prints.

    • After exposure to adhesive tape, fingerprints require careful processing and photographing.

Elimination Fingerprints

  • Importance:

    • Vital to eliminate prints from individuals with legitimate access to a location; enables focus on remaining prints for further investigation.

    • Establish standard forms for elimination; palm prints should be collected on white paper for clarity.

Taking Fingerprints From Decedent

  • Identification through Fingerprints:

    • Essential when missing persons or unable to be identified; may involve latent prints collected from places of employment or home.

    • Rigid fingers require bending joints multiple times for effective collection.

    • Collection methods include using cards to press and roll fingers across the card, or utilizing metal form-fitting devices.

    • Multiple sets of prints (1 for state or federal files and 1 for personal records) are crucial.

Taking Fingerprints From Decedent (2)

  • Challenges:

    • Difficulties arise with decomposed remains, where direct reads become reversed; photographic documentation is essential.

    • For extremely dried-out fingertips, submersion in water may help loosen and restore the ability to take fingerprints.

    • Wrinkled or granulated surfaces may require gentle handling and water injection to smooth out creases for easier collection of prints.

Fingerprint Enhancement – Adobe Photoshop

  • Utility:

    • Helps in enhancing and restoring poor-quality images for investigative purposes.

    • Focus on removing background noise without manipulating original data or altering its integrity.

    • Documentation of enhancements is mandatory for tracking changes; methods should be logged to ensure evidence is admissible in court.

Integrated Automated Fingerprint Identification System (IAFIS)

  • Functionality:

    • Allows for comparison of crime scene fingerprints against a national database.

    • IAFIS can search through several million prints within a matter of minutes, providing critical evidence for investigations.

    • The quality of inked cards and accuracy of IAFIS data entry are critical for achieving correct identifications.

    • Livescan electronic techniques yield standard cards but cannot directly transfer data to IAFIS, necessitating additional identification efforts.

Next Generation Identification (NGI)

  • Overview:

    • Replaced IAFIS in 2011 with enhanced biometric capabilities alongside criminal history tracking.

    • Includes advanced fingerprint identification technology (AFIT), facial recognition searches, and related civil identity searches (licensing, employment, security clearances, military service, and immigration benefits).

Fingerprint Examiner Conclusions

  • Source Exclusion:

    • Conclusion that two friction ridge impressions did not originate from the same source is essential for investigations.

  • Support for Different Sources:

    • Not all assessments yield sufficient support for either proposition.

  • Inconclusive Findings:

    • Situations where prints cannot conclusively be placed as originating from the same or different sources lead to ambiguous findings.

  • Source Identification:

    • The strongest of associations indicates a high degree of support that prints originated from the same source while weakly suggesting otherwise.

ACE-V

  • 4-Step Process:

    • Analysis: Assess if a print is suitable for comparison.

    • Comparison: Analyze characteristics to identify latent and known prints against each other.

    • Evaluation: Derive conclusions based on minutiae present in the prints.

    • Verification: Foster credibility through oversight and confirmation by another examiner.

Final Thoughts

  • Digital Risks:

    • The internet holds unique risks for fingerprint identification, including publicly posted photos of individuals showing high-resolution hand and finger details, sometimes related to criminal activities.

    • Systems like IAFIS can be challenged with counterfeit fingerprints created using 3D printing technology.

    • While rare, the ability to plant fake fingerprints remains a concern.

Activity

  • Engagement with elimination prints is essential for practical experience in this domain.

Images Cited

  • Images sourced from various databases and repositories including Pixabay, Wikipedia, The Body Farm, ShutterStock, and others to illustrate fingerprint processes and techniques.