What are porous and non-porous surface?

1. DIFFERENCE BETWEEN
POROUS & NON-POROUS
SURFACES
Presentedby: Ms. Sanchita Aher
M.Sc. Forensic Science, IFSM
Volunteer at AFRS
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2. CONTENTS:
Introduction
Development of fingerprint over the surface
Non – porous & Porous Surfaces
Fingerprinting in both the cases
Key differences between both
References
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3. INTRODUCTION:
• Fingerprints – impression left behind by the
papillary ridges and furrows present on the tip of
the fingers.
• Significant importance as an evidence –
• Helps identify trait, tracing of an individual.
• unique and different in every individual.
• helps in personal identification.
• Minimum time and efforts
• helps in investigation.
• Permanent
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Ridge
Furrow
Fingerprint pattern

4. DEVELOPMENT OF FINGERPRINT
OVER THE SURFACE:
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Fig 2. Minutiae point –
Bifurcation
Fig 3. Not all complete, clear and
concise formation of the ridges is
observed.
Fig 1. Contact of fingerprint
with the surface.
Fig 1. Ref. www.dailymail.co.uk

5. NON – POROUS & POROUS SURFACES:
Non - Porous Surface
Plastic Glass
Varnished
wood
No penetration of
residues
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Porous Surface
Paper Cardboard
Untreated
wood
Penetration of
residues

6. CHARACTERISTICS OF
FINGERPRINTING IN BOTH THE CASES:
• Fingerprints can be in the form of three types –
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LATENT PRINT
PATENT PRINT
PLASTIC PRINT

7. Fingerprints in case of Non – Porous
surface:
• The sweat and oil residues are deposited over the
surface.
• Susceptible to get damaged.
• Application of powder technique.
• Use of contrast powders.
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Fingerprint over non – porous surface.

8. • Procedure to use powdered technique –
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Use of feathery brush & Red
Fluorescent powder
Removing excess of powder to
make fingerprint ridges visible.

9. • Advanced effective methods – Using cyanoacrylate fuming.
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Whitish coloured fingerprint pattern
Fig 1.
Fig 2.
Fig 1. Ref. www.chm.bris.ac.uk
Fig 2.Ref www.fosterfreeman.com

10. • After development –
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Fig. 1 PHOTOGRAPHY
Fig 2. LIFTING USING
ADHESIVE TAPE
Fig 3. USING MAGNETIC
POWDER
Fig 3. Ref. How to process Latent Fingerprints
using Magnetic Powder – www.youtube.com

11. Fingerprints in case of Porous surface:
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• The sweat and oil residues gets absorbed in the
surface after the deposition.
• Development with chemical methods.
• Chemicals react with the residues.
• Powder methods can’t penetrate into the surface
to develop the print.
• Chemicals: DFO/ninhydrin, iodine, silver nitrate,
etc.
Fingerprint over porous surface

12. • DFO (1,8 – diazofluro-0-one) / Ninhydrin:
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Image ref. www.sciencephoto.com

13. • Iodine fuming –
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Solid crystals into the chamber Yellow – brownish fingerprint
pattern after the development

14. • Silver nitrate –
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Fig. 1. Silver nitrate solution
Fig. 2. Dipping of
specimen sample
Fig. 3. Reddish –brown
fingerprint pattern

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KEY DIFFERENCES BETWEEN
BOTH THE SURFACES:
• Nature of absorbance.
• How long residues remain over the surface?
• Mechanical and chemical methods can be used in
both the cases.
• Why to prefer powder method over non – porous
& chemical methods over porous surfaces?
• Use of unconventional powders.
• Advantage/disadvantage of chemical methods.
• Advantage/disadvantage of powdered methods.
Development of pattern

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REFERENCES:
• Fingerprints: A forensic Tool for Criminal Investigation https://www.legalserviceindia.com/legal/article-2463-
fingerprints-a-forensic-tool-for-criminal-investigation
• Fingerprint Definition & Meaning – Merriam-Webster https://www.merriam-
webster.com/dictionary/fingerprint
• Latent Prints – The Forensics Library https://aboutforensics.co.uk/latent-prints/
• What is a Non-Porous Surface? – Chalkola Art Supply https://www.chalkola.com/blogs/ciy-create-with-
chalkola/non-porous-surfaces
• What is a Non-Porous Material? https://www.reference.com/world-view/non-porous-material-
a49974d247ab202e
• Comparative Study of Different Natural Products For The Development of Latent Fingerprints on Non Porous
Surfaceshttps://www.researchgate.net/publication/306286127_COMPARATIVE_STUDY_OF_DIFFERENT_
NATURAL_PRODUCTS_FOR_THE_DEVELOPMENT_OF_LATENT_FINGERPRINTS_ON_NON_POR
OUS_SURFACES
• Conventional Methods of Latent Fingerprint Development – Forensic Yard
https://forensicyard.com/conventional-methods-of-latent-fingerprint-development/
• BDVA – DFO https://www.bvda.com/en/dfo
• Fuming Cabinet, Ninhydrin Method – Fingerprint: Analysis and Understanding the Science
https://ebrary.net/161565/law/fuming_cabinet

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THANK YOU!
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