Palm Impressions and Distortion

Palm Impressions

  • Palm impressions constitute approximately 30% of all impressions recovered from crime scenes. This significant percentage emphasizes their importance in forensic investigations. Analyzing palm prints can provide valuable evidence that may be crucial in solving cases.

  • Palm orientation is vital because the palm plays a key role in gripping objects. Understanding how the palm is oriented during contact can provide crucial information about the actions performed, offering insights into the events that transpired at the scene.

  • Orienting palm impressions can be particularly challenging, especially when only partial impressions are available. These partial prints often lack key features and reference points, making the analysis more complex and requiring specialized expertise.

  • Unlike fingerprints, palms lack a true pattern for orientation. Palm print analysis relies more on the examiner's ability to interpret various clues, such as flexion creases, ridge flow, and other unique anatomical landmarks.

Parts of the Palm

  • The main parts of the palm include:

    • Thenar Area: Located under the thumb, it's crucial for gripping. This area often provides detailed impressions due to its direct involvement in grasping objects.

    • Hypothenar Area: Situated beside the thenar, it provides balance during grabbing motions. This area contributes to the overall stability and control of the hand.

      • Interdigital Area: Found below the fingers, this region is rich in ridge details that can be highly useful for identification purposes. This area is complex and often exhibits unique characteristics.

Thenar Area

  • Located under the thumb, making it a primary contact point when gripping objects.

  • More bulbous and softer compared to other palm areas. This results in a larger surface area contact, leading to more detailed and distinct impressions.

  • Smudges are common in this area, often due to the pressure applied during gripping. These smudges can sometimes obscure details but can also provide information about the direction of force and aid in orientation.

  • The ridge flow in the thenar area generally flows from the thumb down and away. This pattern assists in distinguishing the thenar area from other regions of the palm.

  • Creases, also known as palmar flexions, interrupt the flow of ridges. These interruptions create unique landmarks that enhance the individuality of the palm print.

  • These creases serve as anchor points, preventing the hand from slipping when force is applied. They are vital for maintaining a firm grip and controlling hand movements.

  • Illustrative analogy: Without these anchor points, the hand would slip, similar to the shearing observed in car accident victims. This puts an emphasis on the importance of creases when it comes to preventing slippage during gripping.

  • Severe trauma cases in car accident victims demonstrate this concept. The shearing forces can cause significant distortion, highlighting the critical role of these anchor points in maintaining hand stability.

  • Crosshatching, where ridge flows intersect, adds complexity. These intersections create unique characteristics within the thenar area, further enhancing its uniqueness.

Hypothenar Area

  • Positioned opposite the thenar area, it balances the hand and contributes to grip stability.

  • Less bulbous and padded compared to the thenar area. This variation results in impressions with varied clarity and detail.

  • Characterized by ridges that curve back out, this distinctive pattern helps differentiate the hypothenar area from other regions of the palm.

  • Features a relatively undisturbed area with flat, slightly arched ridges. This provides reliable reference points for analysis and comparison.

  • Looping formations, including the carpal delta, are significant and useful for comparison purposes in forensic analysis.

  • Ulnar loops are less common, which adds to the uniqueness of this region. Their scarcity makes them a notable characteristic.

  • Ridge flow goes generally from the ulnar side to the radial side, curving over. Understanding this pattern is essential for proper orientation and analysis.

  • Creases can disrupt and redirect ridge flow, creating unique patterns. These alterations contribute to the individuality of the hypothenar area.

Interdigital Area

  • Located between the digits, thenar, and hypothenar areas. This central location makes it a convergence point for various ridge patterns.

  • The variety of ridge cells creates complex and unique impressions. This complexity is valuable for detailed analysis.

  • Pooling areas lead to the formation of deltas, which are key landmarks for orientation and comparison. These deltas serve as focal points during analysis.

  • The general ridge flow starts beneath the index finger, moving towards the little finger. This directional pattern is crucial for determining the print's orientation.

  • Bony parts and flexion creases cause significant ridge path deviations. These deviations contribute to the uniqueness of the area.

  • Delta formations are common and act as focal points for classification purposes. Their presence aids in the identification and categorization of palm prints.

Single loop formations are most common in the little finger area. This is a typical characteristic to be aware of.

  • Whorls are a rare occurrence, which enhances the uniqueness of this region. This scarcity adds to their significance when observed.

  • The carpal delta is located at the base of the hypothenar area, an important landmark for orientation. Recognizing this helps orient the print correctly.

  • Deltas are important for initial palm orientation. They guide the subsequent steps in the analysis process.

  • Palm impressions have been actively and intentionally searched for since 2002/2003. This timeline marks a shift in forensic practices, where palm prints gained recognition.

Palmar Flexion Creases

  • Three main creases:

    • Distal transverse: One out of three of the main creases on a palm.

    • Proximal transverse: One out of three of the main creases on a palm.

      • Radial longitudinal: Of

  • Creases are permanent, reliably observed, and serve as reference points. Their consistency makes them valuable for analysis.

  • Creases are set at six weeks gestation, which underscores their significance in individual identification. Given their origin so early in gestation showcases their important when it comes to identifying people.

  • The distal transverse crease is the highest of the three.

Distal Transverse Crease

  • Starts from the thumb side, making it a key identification feature. You'll find that it can be identified it starts from the thumb side.

  • Differentiates hypothenar and interdigital areas, serving as a boundary. It separates these two key areas of the palm.

Proximal Transverse Crease

  • Constant and broad presence makes it a reliable landmark. Given how broad it is, it can be used as a landmark

Radial Longitudinal Crease

  • Separates thenar and hypothenar areas, essential for regional distinction. Having a strong separation makes it easier to distinguish this section from the other.

  • Named 'radial' because of alignment with the radius bone. It is named this way because it is a direct alignment.

  • High deviation density adds uniqueness. Lots of deviations makes this that much more unique.

Creases in the Thenar Area

  • Significant, temporary creases add to this diverse area.

  • Only three permanent:

    • Distal transverse

      • Proximal transverse

    • Radial longitudinal

  • Transient creases vary and are less reliable. Don't rely as much on transient creases because they are subject to change often.

  • Aging affects crease appearance. Expect to see that as one ages, their creases will show more easily.

Creases in the Hypothenar Area

  • Least amount of creases gives a smoother appearance.

  • Location More on finger side.

  • Padded nature is linked to crease number/arrangement.

Thenar vs. Hypothenar Creases

  • Crosshatching is common in the thenar, distinguishing it from the hypothenar area. This unique characteristic makes it very easy to distinguish from the other.

  • Hypothenar crosshatching indicates thenar presence. Finding crosshatching indicates also the other part's presence.

Creases in the Interdigital Area

  • Understanding creases in the interdigital area is very minor.

Palm Impression Study

  • Goal: Gain nomenclature knowledge and grasp ridge flow/creases.

Key Aspects

  • Nomenclature: Understand palm area terms for accurate analysis.

  • Nomenclature of Creases: Accurate identification is key for comparison.

  • Uniqueness and Persistency: Friction ridges are valuable for ID because of this.

  • Crease Identification: Creases alone do not give sufficient detail for + ID.

    • you are not allowed to eliminate purely on creases.

Embryology

  • Flexion creases are visible at eight weeks gestation, demonstrating their key role hand function.

  • Hand movement starts at 11-12 weeks influencing crease development for sure.

  • The hand takes shape between 6-10 weeks.

  • Sequence: Hand shape comes first, after which crease form, then friction ridges.

  • Major creases link with volar pad formation.

  • Palmar grasping starts at twelve weeks refining creases.

Timelines

  • Refer to Kimura and Kitagawa’s timelines

Genetics

  • Patterns are linked to heredity.

  • - But genes/hereditary patterns aren't that important because that could change.

  • Major flexion increases are linked towards monozygotic and dizygotic twins.

  • patterns are linked to heredity; the genes are hereditary patterns

  • Mono creases can also be observed and tested; monocreases are also a possibility

Flexion Creases

  • You’re never allowed to do crease comparisons, but you can use them to roughly locate the area.

    • flexions

Persistency

  • The major ones are consistent; the minor ones aren’t and you need to be aware of that.

Palm Impressions - Assignments

This Week Assignment

  • Topic: Wrongful Convictions by Fingerprints

  • Length: 1-2 page research paper

  • Content: Analyze exonerated cases based on fingerprint evidence.

  • Restriction: Do not use Brandon Mayfield.

  • Focus: Errors, initial/subsequent expert analysis differences, causes (human error, biases, tech).

  • Emphasis: Preventing future mistakes; responsibilities in forensic work.

Next Week Assignment

  • Topic: Fingerprint Distortion Video (Skin Flick)

  • Task: Video demo friction ridge movement with varying pressure:
    -