Keywords

9.1 Introduction

‘Palm’ refers to the inner surface of the hand, and ‘palmprints’ are the prints formed by the inner surface of the hand. The terms ‘palmprint’ and ‘handprint’ cannot be used interchangeably as the handprint includes the print of the whole hand, including the print of the fingers and thumb phalanges, while the palmprint is a portion of the ventral part of the hand (Gopal et al. 2016). Handprints and palmprints are often encountered at the crime scene. Handprints can provide information such as the stature of the person (Krishan et al. 2015), sex (Kapoor and Badiye 2015a; Jerković et al. 2021; Dayarathne et al. 2021), determination of hand (Kapoor and Badiye 2015b; Kapoor et al. 2020), and personal identification. Palmprints can also play a significant role in differentiation between left and right hands, determination of sex (Badiye et al. 2019), personal identification, and presence of any abnormalities in the palm. Handprints and palmprints can be encountered in crimes like burglary, theft, kidnapping, sexual assaults, etc., on various surfaces. Just like fingerprints, palmprints can be used for the identification of suspects, as palmprints are also unique and persistent (Fig. 9.1).

Fig. 9.1
An image displays inked prints of the inner part of the left and right hands.

Inked handprints of left and right hand

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Generally, the palmprint is divided into three groups: interdigital area (area below the fingers), thenar area (area near thumb), and hypothenar area (area near little finger). Palmprints have some characteristic features; thus, even when partial prints are collected from the crime scene, they may provide helpful information (Fig. 9.2).

Fig. 9.2
A print of a palm. It consists of 3 regions, thenar, interdigital, and hypothenar. The regions are differentiated with a T-shaped boundary in between.

Three palmar regions: interdigital, hypothenar, and thenar

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9.2 The Emphasis on Palmprints over Fingerprints

Palmprints are similar to fingerprints as they are unique for every individual; even monozygotic twin does not have the same palmprints. They are persistent throughout human life and have ridge details similar to fingerprints. Fingerprints are smaller in size and thus may have more probability of getting smudged prints. However, palmprints have a larger surface area than fingerprints; thus, the ridge details are better appreciated. Palmprint also has unique characteristics like principal lines, tri-radii, etc., which can be used for classification and identification purposes.

9.3 Regions of Palm

  • Interdigital Region

    The interdigital region shows many ridge details. The primary ridge flow starts from the bottom of the index or middle finger, runs in the interdigital region, and exits the palm from the ulnar side. This characteristic feature is called a “waterfall” (Fig. 9.3). Usually, the interdigital areas have four deltas located below each finger. However, palmprints may have less or more than four deltas (Maceo et al. 2013). The delta below the index finger is termed “clean delta,” the delta below the middle finger is termed “snow cone delta,” the delta below the ring finger is called “double snow cone right/left,” and the delta below the little finger is known as “side cone” (Horton 2018). The most common patterns found in the interdigital region are loop and whorl; other than that, patterns like column and tented arch are also observed (Horton 2018). The interdigital region can be divided into VP regions: the region between the index and middle fingers, the region between the middle and ring fingers, and the region between the ring and little fingers as II, III, and IV, respectively (Maceo et al. 2013) (Fig. 9.4).

  • Thenar

    The thenar region is the area below the thumb of the palm. The thenar region has two characteristic features, namely, half-moon and vestiges. The ridges entering the palm through the middle of the index finger and the thumb and leaving from the bottom of the print give rise to a semi-circle formation around the thumb and is called a “half-moon.” Another characteristic feature of the thenar area is the vestige. The vestiges run perpendicular to the pattern’s normal ridge flow and are usually found at the base of the thumb. Vestiges are only found in thenar region; thus, it can be very helpful in partial palmprint examination to understand the orientation of the hand as well as differentiation between right and left hand. Vestiges are also called “thenar area clues” (Horton 2018). Vestiges may be small and independent. However, this region may also show patterns such as loop, column, and whorl (Maceo et al. 2013). Another region called the flip area is located in the web area. These ridges change the flow direction as they flip up, thus termed as “flip area” (Horton 2018) (Fig. 9.5).

  • Hypothenar Region

    The hypothenar area covers the most significant part of the palm, and thus, it is primarily present in most partial palmprints. The ridges show a downward movement and exit from the side of the hand. The portion of the ridges in the hypothenar region tends to converge and appears as a funnel, thus termed as “funnel area.” “Belly out” regions are at the bottom of the hypothenar area, where the ridges running down the pattern make a turn and exit the palm through the side of the hypothenar region. The ridges flowing in the vertical direction form a delta at the lower portion of the palm. It is termed the “carpal delta” and is mainly formed between the thenar and hypothenar regions. A slight arch below the carpel delta is called a “hump.” The most common pattern found in the hypothenar region is a loop. The loop pointing towards the outer edge of the palm is called the “ulnar loop,” while the “radial loop” points towards the center of the palm. The loop pointing toward the bottom of the palm is called a “proximal loop” (Maceo et al. 2013; Horton 2018) (Figs. 9.6, 9.7, and 9.8).

Fig. 9.3
An image of the impressions of the left and right palms. A non-inked region is present at the center portion of each impression.

Waterfall region of interdigital region of left and right hand

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Fig. 9.4
An image of the impression of a right palm indicates the interdigital region. The impressions of the index, middle, ring, and little finger are also present.

Interdigital region of right palm showing the index (I), middle (M), ring (R), and little (L) deltas

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Fig. 9.5
An image of an inked impression of the right palm. The thenar area is present at the base of the thumb.

Thenar area of right hand

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Fig. 9.6
An impression of the right palm. The funnel region extends from the index finger to the small finger.

Funnel area of the right hand

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Fig. 9.7
An image of the impression of the right palm. An inverted funnel-shaped structure is sketched toward the base.

Outline of the belly out portion of the right hand

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Fig. 9.8
An image of the impression of the right palm. An inverted funnel-shaped structure is sketched toward the base. The funnel consists of 2 parts, the carpal delta and the hump.

The carpal delta and hump areas of the palm of the right hand

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9.4 Classification of Palmprints

Classification of palmprints is very helpful for documenting and comparing complete and partial prints. Some palmprint classification systems are given below.

9.4.1 Western Australian Palmprint Classification

  • Primary Classification

    The primary classification is based upon the ridge flow in the palm’s three regions, i.e., interdigital, thenar, and hypothenar regions. The values assented to the areas are similar to the Henry classification, but this classification provides numerical values irrespective of the type of pattern present. Furthermore, in the end, one is added to the total score (Table 9.1).

  • Secondary Classification

    The secondary classification has two divisions. The first division is based on the patterns present in the thenar and hypothenar areas. And the values are expressed in the form of fractions with thenar values in the numerator and hypothenar values in the denominator. The second division (secondary subclassification) deals with the area between the thumb, index finger, and interdigital area (Holder et al. 2011). Therefore, the classification formula becomes

    $$ \left(\mathrm{primary}\right)=\left(\mathrm{thenar}\right)\ \left(\mathrm{thumb}\ \mathrm{to}\ \mathrm{index}\ \mathrm{area}\right)/\left(\mathrm{hypothenar}\right)\ \left(\mathrm{interdigital}\right). $$
Table 9.1 Primary value determination (Baird 1959, pp 21–24)
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9.4.2 Liverpool Palmprint Classification System

The Liverpool classification system is based on three divisions of palm, similar to the Western Australian Palmprint Classification system; however, the Liverpool classification system has four parts and is represented in alpha numeric symbols.

  1. 1.

    Primary Division

    The primary division has three parts thenar, hypothenar, and interdigital. In cases when more than one pattern is present in the palmer area, it is considered as one pattern. While in cases when the patterns are present in different palmer areas, all the values are added together. Value pattern indications are represented in Table 9.2.

  2. 2.

    Secondary Division

    The secondary classification is based upon the ridge patterns present in the hypothenar region of the palm. Table 9.3 represents the symbols for each pattern observed in the hypothenar region. In the secondary subclassification, the ridge characteristics are recorded when a single loop is present in the hypothenar area. And in case of absence of any pattern, type of delta is recorded.

  3. 3.

    Tertiary Division

    Tertiary division is considered for the patterns in the thenar area. If two patterns are present in the thenar region, the coding box is divided into two parts by a diagonal line from the lower-left corner to the upper right corner of the box. Moreover, the pattern present near the interdigital area is represented by an alphabetical symbol in the upper left triangle. The pattern near the thenar region is represented by an alphabetical symbol in the lower-left triangular box of the coding box.

  4. 4.

    Quaternary Division

    The quaternary division is based on the patterns observed in the interdigital region of the palm. It sub-divided into three parts. Part 1 represents the pattern present in the interdigital area. Part 2 provides a numerical value to the pattern in relation to the fingers (Table 9.4). Part 3 involves recording the ridge count for arch and loop patterns.

Table 9.2 Pattern indication from primary value
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Table 9.3 Symbols used in the secondary classification in the Liverpool Palmprint Classification System
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Table 9.4 Pattern value for part 2 of the quaternary division
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The complete classification system of the Liverpool palmprint classification is represented within a coding box, and the patterns are mentioned in the coding box as alphanumeric symbols (Table 9.5).

Table 9.5 Coding box for Liverpool Palmprint Classification System
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9.4.3 The Brogger Moller Palmprint Classification System

The Brogger Moller Palmprint Classification System employs a special measuring glass with four separate measuring areas. Each area has three concentric circles with 2, 4, and 6 cm radii. This classification system involved patterns present in three regions of palm and primary, secondary, and tertiary values (Tables 9.6, 9.7, and 9.8). And the measuring glass was used to determine some values as represented in the table below (Holder et al. 2011).

Table 9.6 Classification for the hypothenar (Moenssens 1971, pp 200–205)
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Table 9.7 Classification for the interdigital (Moenssens, pp 206–207)
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Table 9.8 Classification for the thenar (Moenssens, pp 207–209)
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9.4.4 Palmprint Classification Using Principal Lines

The principal lines have been used to classify a palmprint. The print can be classified into six categories based on the principal lines and intersections. To classify the print, the principal lines are defined, and the number of principal lines and intersections are counted (Wu et al. 2004) (Table 9.9).

Table 9.9 Palmprint classification system based on principal lines and intersections
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9.4.5 Automated Palmprint Classification Systems

Some authors have worked in the area of automated palmprint identification systems (Chen et al. 2001; Duta et al. 2002; Funada et al. 1998; Li et al. 2002; Sowmiya Manoj and Arulselvi 2021; Wu et al. 2002; Zhang and Shu 1999). Sakdanupab and Covavisaruch (2008) provided an automated palmprint classification system based on extraction of the heart line, head line, and life line. Scanned palmprints were overlaid in the computer system and compared by automated tools (Connie et al. 2005). The FBI has initiated a process to collect and convert into digital format to maintain a digital library (Holder et al. 2011).

Case Study:

Automated systems aid in comparing the unknown print with the database and finding the matching print. AFIS has helped in solving many crimes. A case was reported of a break-in into a business, and lateral palmprints were found on the entrance lock. The prints were developed using magnetic powder, and a scanned copy was run in the AFIS to find the match. However, no result was found. A few months later, fingerprints and palmprints of a suspect were collected and compared with the unknown lateral palmprint, and it was found to be a positive match. It was found that the suspect’s record already exists but due to lack of sufficient amount of ridge details of lateral palmprints, it was not detected (Hefetz et al. 2021).

9.5 Conclusion

The study of palmprints holds immense potential in identifying individuals and assisting in criminal investigations. Palmprints, with their intricate patterns and distinctive features, offer a wealth of information for forensic analysis. The subsequent exploration of the regions of the palm highlights the complex nature of palmprints. The various parts, including the thenar, hypothenar, and interdigital areas, each possess distinct characteristics that contribute to the overall identification process. Understanding these regions’ specific details and patterns is vital for accurate palmprint analysis.

Overall, the chapter emphasizes the unique nature of palmprints as a valuable forensic tool. Forensic experts can extract crucial information for individual identification and crime scene analysis by examining the handprints' regions and employing classification systems. As technology advances, palmprint analysis promises to play an increasingly integral role in forensic investigations, enhancing our ability to solve complex cases and bring justice to those affected.