A. As the adhesive forces are in inverse proportion to tempera-
`ture. on touching or holding different objects the fiat sticks to
`them quite well because in most cases those objects are cooler
`than the human body.
`
`B. Besides the temperature, adhesive forces are affected by sur-
`face structure, too. The rougher the surface, the bigger the
`adhesive forces. Because of that, when fresh fingerprints on
`varnished or polished surfaces are being developed with pow-
`ders, they can be easily deleted and destroyed. This means that
`in such cases much more attention and caution must be paid
`than when processing prints left on rougher surfdces.
`
`C. In contrmt to fat, the perspiration drops are conjectured to be
`affected by electrostatic forces of the print receptive surface.
`This conjecture is explained as follows: Firstly, the surface
`molecules or ions of a given object usually possess unbalanced
`electrostatic forces and these provide the surface with a net
`charge; secondly, sweat represents an electrostatic system with
`an anisotropic charge distribution.
`
`Between those unbalanced forces of the print receptive surface and
`the electrostatic forces of sweat, a potential difference, called absorp-
`tion potential, originates. This is responsible for the transfer and reten-
`tion of palm sweat on different objects.
`
`II. Effect of Different Surfaces
`What kinds of processes involving the excreted perspiration-~dtty
`secretion occur under the influence of different surfaces? Do any par-
`ticular changes occur in the compositional quality of perspiration and
`fat? Are there any chemical reactions between the print receptive sur-
`face and the print origination substances?
`
`Those questions can be answered only if each surfact is approached
`separately, in accordance with its physico-chemical and structural fea-
`tures.
`
`F
`
`.
`
`Fingerprints and Factors Affecting
`Their Condition
`
`Kostadin Bobev
`
`Research Institute of Forensic Science and Criminology
`Sofia, Burgaria
`
`Abstract: The origin of latent fingerprint~ represents a physico-chemical process on
`the border or contact area between the skin relief and print receptive surface. In thi$ sense
`the mechanism of latent fingerprint origins depends on a number of surface phenomena.
`Thi\ report pre$ents ob~ervation~ made on different $urfaces under different phy~ical
`conditions.
`
`I. Mechanism of Fingerprint Deposition (Sweat and Fatty Sub-
`stances)
`The perspiration-fatty secretion (i .e., secretions from perspiration or
`sweat and from fatty substances like lipids) on the surface of the hands
`can be described as follows. Fat covers almost the whole sutidce of
`papillary lines without penetrating into the space between them and
`into the channels of sudoriferous glands. The fat retention on the skin
`relief of hands is conjectured here to be due to the physical phenome-
`non of adhesion, the force of attraction between molecules of solid,
`liquid or gaseous substances which manifests itself on contact between
`objects. At the same time the sweat, periodically excreted by the sudo-
`riferous glands in the form of clear drops, is conjectured here to be kept
`in the pore hollows by surf%ce tension.
`
`What happens to the sweat and Fdts when the fingers touch a solid
`surface? The fat as well as the perspiration which comes in contact
`with the surface often get transferred to the surface according to the
`following schemes:
`
`II
`
`J. Forensic Ident.
`176/45 (2), 1995
`
`Reactive Surfaces Ltd. LLP
`Ex. 1043 (Ray Attachment I)
`Reactive Surfaces Ltd. LLP v. Toyota Motor Corp.
`IPR2016-01914
`
`J. Forensic Ident.
`45 (2), 1995\ 177
`
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