Examination of Phalangeal Friction Ridge Flow Trends
UTS Primary Supervisor: Dr. Xanthe Spindler
NSWPF External Supervisors: Andrew Chapman, Michael Whyte, Joshua Thompson
Centre for Forensic Science, University of Technology Sydney, Broadway
Chloe George
Unlike the friction ridge skin on the fingertips, palms and even the soles of the feet, the friction ridge skin on the medial and proximal phalanges has been little studied
Review of the Literature
What do we know?
Smith, R. 2009, Demystifying Palm Prints, pp.39
Smith, R. 2005, Demystifying Palm Prints, pp.40
"Although empirical studies have not been conducted on this subject, there are several consistencies that can be used very successfully used for orientation purposes”
‘Down and Out’ Ridge Flow
‘Wavy’ Ridge Flow
Ploetz-Radmann’s Phalangeal Classification System
Marie Ploetz-Radmann’s 1937
‘Skin Ridge Patterns of the Lower Two Phalanges of the Human Hand’
Considerations with Prior Research
Ploetz-Radmann published 85+ years ago
Dated
Anthropologically-Directed
Obscurity of text
Aims and Research Questions
Aims and Research Questions
3
2
1
Aim: Validate Ploetz Radmann’s study to determine whether consistent universal trends exist in the ridge flow on the phalanges of the fingers
Can the friction ridges on the middle and proximal phalanges be classified into patterns?
Are there trends in the distribution and frequency of patterns found on the phalanges?
Are there trends in the direction of ridges on the phalanges of the fingers?
Materials and Methods
Methodology
Fingerprint Collection
Pattern classification
Statistical Analysis
Using Ploetz-Radmann’s classification system
Data Collection
1. Black Fingerprint Powder + White Adhesive Lift + Transparent Sheet
2. Fingerprints Provided by the NSWPF
207 Participants = 5796 phalangeal prints
All fingerprints deidentified
Ethics Approval Number: ETH18-2521
Ploetz-Radmann’s Classification system
12 Pattern Types
1. Stripe
A group of straight, parallel ridges that can be either diagonal or horizontal
2. Hook
Similar to Stripe except the ridges start or end with a small curve or ‘hook’
3. Bow
Ridges form a curve/arch horizontally across the phalange
4. Wave
A wave, as it sounds, consists of two arcs joined together
Typically flows horizontally
5. Angle
Two directions of ridges meet at an angle.
One set of ridges run parallel to finger creases
The other set of ridges run diagonally
6. Arc Angle
Similar to Angle except ridges running parallel to creases will form a curve or an ‘arc’
7. Double Angle
The double angle pattern, as it sounds, is the combination of two angles
8. Double Arc Angle
The combination of two arc angles
9. Double Sheet
Two arcs/curves meeting back to back
Often in the approximate midline of the phalange
10. Inclusion
Typically contains a spindle-shaped core
Can be completely enclosed or opened to the left or right side
11. Feather
Arrangement of acute to obtuse angles forming horizontally across the phalange.
Image gathered from: Ploetz-Radmann, M 1937, ‘Hautleistenmuster der unteren beiden Fingerglieder der menschlichen Hand’, Zeitschrift für Morphologie und Anthropologie, vol. 36.
12. Rare
Any pattern that could not be classified into previous 11 patterns
Ploetz-Radmann’s Phalangeal Classification System
Images gathered from: Ploetz-Radmann, M 1937, ‘Hautleistenmuster der unteren beiden Fingerglieder der menschlichen Hand’, Zeitschrift für Morphologie und Anthropologie, vol. 36, pp. 281-310.
Stripe (S)
Hook (H)
Wave (WI)
Bow/Arch (B)
Angle (N)
Arc Angle (AN)
Double Angle (DN)
Double Arc Angle (DAN)
Double Sheet (C)
Inclusion (C)
Feather (C)
Rare (C)
Compound/Combination
1
2
4
3
5
6
7
8
9
9
10
11
12
Ridge Direction
Right hand perspective
Radial
Ulnar
Transverse
Distal-Radial
Distal-Ulnar
Proximal-Radial
Proximal-Ulnar
Proximal
Distal
Stripes and Compound
Double Angles and Double Arc Angles
Waves
Bows
Hooks, Angles and Arc Angles
Radial
Ulnar
Results
Distribution and Frequency of Patterns
Population Frequencies of Patterns
Frequency of Patterns on Individual Fingers
Distribution and Frequency of Patterns
Frequency of patterns on medial phalanges
91.45% of all Arc Angle patterns occur on the medial phalanges
92.6% of all Double Angle patterns occur on the medial phalanges
100% of all Double Arc Angle patterns were found on the medial phalanges
85.66% of all Angle patterns occur on medial phalanges
Distribution and Frequency of Patterns
Frequency of patterns on proximal phalanges
87.6% of all combination patterns occur on the proximal phalanges
77.03% of all stripe patterns occurred on the proximal phalanges
75.68% of all wave patterns occur on the proximal phalanges
73.30% of all hook patterns occur on the proximal phalanges
Distribution and Frequency of Patterns
Ridge Direction Trends
Right hand perspective
Ridge Direction Trends
'Down and Out’ ridge flow on ‘outer fingers’: Thumb, Index & Little and Left Ring Fingers
More variety of directions on inner fingers
Ridge Direction Trends
Ridge Direction Trends
54% of directions are ulnar-oriented
30% of directions are radial-oriented
Left hand shows a slight trend towards an ulnar direction
56% of directions are radial-oriented
31% of directions are ulnar-oriented
Right hand shows a slight trend towards a radial direction
LEFT HAND
RIGHT HAND
Statistical Tests of Significance
Moods Median Test
Population Medians
Were population medians equal for:
Chi-Square Test
Association Between Two Variables
Is there an association between pattern type and:
Population Medians – Moods Median Test
Pattern-type vs. Finger
Pattern-type vs. Phalange
p<0.05 = reject null hypothesis
Population medians are not all equal
Association Between Two Variables - Chi-Square Test
Pattern and Phalange
Pattern and Hand
Pattern and Finger
p<0.05 =
reject null hypothesis
Null hypothesis Ho: The two variables are not associated
Alternative hypothesis H1: The two variables are associated
There is an association between pattern and: phalange, finger and hand
Discussion & Conclusion
Operational Uses
Search Heuristics
Training Fingerprint Practitioners
1
2
Search Heuristics
Finger Nomination
Results can assist examiners to narrow down a search by nominating a finger(s), or hand (left or right) for their searches
Can be used in conjunction with distal phalanges
Search Heuristics
1
Training Fingerprint Practitioners
'A lack of training and experience can affect an examiner's ability and confidence in determining proper orientation of partial latent prints’ - Ron Smith (2005)
Training Fingerprint Practitioners
2
Knowledge of typical patterns/phalangeal ridge flow can:
Forensic examiners now have information relating to features of 3 areas of friction ridge skin
Limitations & Future Direction
Population design
All fingerprints de-identified - can’t be sure whether we have a representative population in terms of age, ancestry and gender
Different collection methods
2 fingerprint collection methods utilised. Handprints resulted in large number of unclassified phalanges of the thumb
Classification System
Classification system proposed by Ploetz-Radmann (and used in this study) could be refined to make it more user friendly in a forensic science context.
Conclusion
Ploetz-Radmann’s article has shown that phalange ridge flow can be classified into distinct patterns
There are observable trends in both pattern frequency and distribution and ridge direction
Results of this study can aid in determining finger nomination and orientation
Acknowledgements
Xanthe Spindler, Scott Chadwick, Anjali Gupta
Andrew Chapman, Michael Whyte, Joshua Thompson, Jennifer Raymond
Thank you to the donors who provided their fingerprints
�Thank you for your time and attention��Questions?
Email: geor1chl@police.nsw.gov.au