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Fingerprint sampling devices; Methods for controlling fingerprint deposition

Fingerprint sampling devices; Methods for controlling fingerprint deposition. Dr Sarah Fieldhouse Ph.D. Fingerprint research. Latent mark detection. They all require ‘fingerprints’. Latent mark development/recovery techniques. Friction ridge skin identification.

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Fingerprint sampling devices; Methods for controlling fingerprint deposition

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  1. Fingerprint sampling devices; Methods for controlling fingerprint deposition Dr Sarah Fieldhouse Ph.D.

  2. Fingerprint research Latent mark detection They all require ‘fingerprints’ Latent mark development/recovery techniques Friction ridge skin identification ‘fingerprint’ research There are no universally accepted protocols for carrying out ‘fingerprint’ research. Latent mark composition Advancement of AFIS Latent mark longevity

  3. Examples of existing strategies to control fingermark deposition • asking participants to apply ‘moderate pressure’ [1] • asking participants to carry out specific tasks [2] • researcher assisted deposition [3] • 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]

  4. Variations in fingermark deposition 1. Variations in force application 3. Variations in contact area of friction ridge to surface contact 4 inked fingerprints deposited by the same finger 2. Variations in contact time between the ridges and the substrate

  5. Adjustable finger clamp Deposition platform Finger resistor bar 110mm Finger Rest Deposition force management springs 145mm The fingerprint sampler The fingerprint sampler allows consistent and reproducible fingermark deposition, controlling physical factors associated with deposition [6].

  6. Fingermarks deposited using the fingerprint sampler • 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]

  7. There were two aims to this research project; To develop a fingerprint sampler to facilitate fingermark deposition at different force quantities. To study the effects of different force applications during latent fingermark deposition on the appearance of the resultant marks.

  8. Finger rest 190mm Fingerprint deposition platform Force scale 290mm Fingerprint sampler 2 Direction of movement Adjustable base Multiple force capability

  9. Finger rest Fingerprint deposition platform 110mm Spring Fingerprint sampler 2

  10. Spring calibration Hooke’s law of elasticity

  11. 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.

  12. Results - Scanning Electron Microscopy 1N 5N 10N

  13. Results - Surface plot analysis 2N 1N 3N 4N

  14. 6N 5N 8N 7N

  15. 9N 10N 10N 5N 1N

  16. Results - Differences in surface area 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).

  17. Results - Differences in surface area 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).

  18. Conclusions 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. As the force applied to the finger increases; • the surface area of the resultant mark increases (to a maximum point), especially important with marks deposited under less force. • the quantity of friction ridge residue transferred to the resultant mark appears to increase, as does ridge depth. This may affect; • how the latent mark develops and how a mark is assessed. • the consistency of samples in research projects • important for fingermark comparisons, e.g. how they change over time

  19. 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.

  20. Further information Dr Sarah Fieldhouse (Staffordshire University), email: s.j.fieldhouse@staffs.ac.uk telephone: 01782 295795 Philip Morton (SciChem), email: philip.morton@scichem.com telephone: 07522 428611 Thank you for listening, any questions?

  21. 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.

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