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D R S A R A H F I E L D H O U S E P H . D .Fingerprint sampling devices; Methods for controlling fingerprint deposition
Friction ridge skin
identification
Advancement of AFIS
Latent mark detection
Latent mark longevity
Latent mark composition
Latent mark development/
recovery techniques
‘fingerprint’ research
Fingerprint research
There are no universally
accepted protocols for carrying out ‘fingerprint’
research.
They all require ‘fingerprints’
asking participants to apply ‘moderate pressure’ [1]
asking participants to carry out specific tasks [2]
use of a top pan balance to apply a specified mass, which is then converted to force [4, 5]
use of a fingerprint sampler to control deposition [6]
Examples of existing strategies to control fingermark deposition
researcher assisted deposition [3]
1. Variations in force application
2. Variations in contact time between the ridges and the substrate
3. Variations in contact area of friction ridge to surface contact
Variations in fingermark deposition
4 inked fingerprints deposited by the same finger
145mm
Deposition force management springs
110mmFinger resistor bar
Deposition platform
Adjustable finger clamp
Finger Rest
The fingerprint sampler
The fingerprint sampler allows consistent and reproducible fingermark deposition,
controlling physical factors associated with deposition [6].
• Consistency in surface area• Contact time controlled• No distortion associated with mark deposition, e.g. force• Improved ‘quality’ of marks compared to marks deposited without it’s use [6]
1 2 3 4 5
6 7 8 9 10
Fingermarks deposited using the fingerprint sampler
There were two aims to this research project;
1. To develop a fingerprint sampler to facilitate fingermark deposition at different force quantities.
2. To study the effects of different force applications during latent fingermark deposition on the appearance of the resultant marks.
Adjustable base
Finger rest
290mm
190mm
Fingerprint deposition platform
Force scale
Direction of movement
Fingerprint sampler 2
Multiple force capability
Fingerprint sampler 2
Spring
Fingerprint deposition platform
Finger rest
110mm
Hooke’s law of elasticity
0
0.5
1
1.5
2
2.5
f(x) = 0.387492659077273 x + 0.019999740151347R² = 0.999999999845224
Force (N)
Sp
rin
g d
efle
ctio
n (
cm)
Spring calibration
Methodology
1. Latent and inked fingermarks were deposited from the same finger at approximate force quantities of 1N-10N at 1N increments onto glass surfaces and photocopier paper.
For latent fingermarks participants were asked to refrain from washing their hands for 1 hour prior to deposition. The fingers were ‘loaded’ against an equivalent area of friction skin, i.e. a finger.
2. The latent fingermarks were then examined using Scanning Electron Microscopy.
3. The latent fingermarks were then developed using CNA fuming
4. Surface plot analysis commenced using a fingerprint digitiser (DCS121)
5. The inked fingerprints were examined for differences in surface area at different forces and consistency between marks at equivalent forces.
Results - Scanning Electron Microscopy
1N 5N 10N
Results - Surface plot analysis
1N
3N
2N
4N
5N 6N
7N 8N
9N
10N1N 5N
10N
Results - Differences in surface area
12.0
13.0
14.0
15.0
16.0
17.0
18.0
19.0
20.0
21.0
22.0
23.0
24.0
1 2 3 4 5 6 7 8 9 10
Len
gth
(mm
)
Force (N)
Fingerprint length
participant 1 participant 2 participant 3 participant 4 participant 5
Standard Error of the Mean = 0.5mm
Statistically significant differences were found to exist (N15, F72.485, p 0.00). Effect size large (0.838).Bonferroni post hoc tests suggest that these exist between the earlier force increments only. (p≤0.05).
Results - Differences in surface area
5.06.07.08.09.0
10.011.012.013.014.015.016.017.0
1 2 3 4 5 6 7 8 9 10
Len
gth
(mm
)
Force (N)
Fingerprint width
participant 1 participant 2 participant 3 participant 4 participant 5
Standard Error of the Mean = 0.5mm
Statistically significant differences were found to exist (N15, F99.622, p 0.00). Effect size large (0.877). Bonferroni post hoc tests suggest that these exist between the earlier force increments only. (p≤0.05).
Conclusions
As the force applied to the finger increases;
• the quantity of friction ridge residue transferred to the resultant mark appears to increase, as does ridge depth.
• how the latent mark develops and how a mark is assessed.
• the surface area of the resultant mark increases (to a maximum point), especially important with marks deposited under less force.
Differences in the quantity of force applied by friction ridge skin to a surface during mark deposition will affect the appearance of the resultant marks.
This may affect;
important for fingermark comparisons, e.g. how they change over time
• the consistency of samples in research projects
Implications for fingerprint research
As part of a scientific approach to research it is important to recognise and control variables where possible.
Fingerprint samplers represent a simple means of controlling physical variables associated with fingermark deposition.
This approach might help to improve efficiency in the research approach.
Fingerprint samplers can be useful teaching aids.
Further information
Dr Sarah Fieldhouse (Staffordshire University), email: [email protected] telephone: 01782 295795
Philip Morton (SciChem), email: [email protected] telephone: 07522 428611
Thank you for listening, any questions?
References
[1] Bohanan, A. M. (1998). Latent’s from Pre-pubescent Children Versus Latent’s from Adults. Journal of Forensic Identification. 48(5) p570-573.[2] Given, B. W. (1976). Latent Fingerprints on Cartridges and Expended Cartridge Cases. Journal of Forensic Sciences. 21(3) p587-594.[3] Croxton, R. Baron, M. Butler, D., Kent, T., Sears, V. (2010). Variation in amino acid and lipid composition of latent fingerprints. Forensic Science International. 199(1-3 p93-102.[4] Fieldhouse SJ. (2009) Consistency and reproducibility in the deposition and evaluation of latent fingermarks, contributing to an investigation into the effectiveness of a portable cyanoacrylate fuming system and aluminium powder for latent fingermark development (A thesis submitted in partial fulfilment of the requirement of Staffordshire University for the degree of Doctor of Philosophy). Stoke on Trent: Staffordshire University.[5] Jasuja, P., Toofany, M. A., Singh, G., Sodhi, G. S. (2009). Dynamics of latent fingerprints: The effect of physical factors on quality of ninhydrin developed prints – A preliminary study. Science and Justice. 49(8).[6] Fieldhouse, S., 2011. Consistency and reproducibility in fingermark deposition. Forensic Science International. 207(1-3) p96-100.
