Accepted Manuscript

Title: Understanding Physical Developer (PD): Part II–Is PDTargeting Eccrine Constituents?

Author: Mackenzie de la Hunty Sebastien Moret ScottChadwick Chris Lennard Xanthe Spindler Claude Roux

PII: S0379-0738(15)00407-7DOI: http://dx.doi.org/doi:10.1016/j.forsciint.2015.08.029Reference: FSI 8158

To appear in: FSI

Received date: 11-7-2015Revised date: 25-8-2015Accepted date: 31-8-2015

Please cite this article as: M. de la Hunty, S. Moret, S. Chadwick, C.Lennard, X. Spindler, C. Roux, Understanding Physical Developer (PD): PartIIndashIs PD Targeting Eccrine Constituents?, Forensic Science International (2015),http://dx.doi.org/10.1016/j.forsciint.2015.08.029

This is a PDF file of an unedited manuscript that has been accepted for publication.As a service to our customers we are providing this early version of the manuscript.The manuscript will undergo copyediting, typesetting, and review of the resulting proofbefore it is published in its final form. Please note that during the production processerrors may be discovered which could affect the content, and all legal disclaimers thatapply to the journal pertain.

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Understanding Physical Developer (PD): Part II – Is PD Targeting Eccrine Constituents?

Authors: Mackenzie de la Hunty1*, Sébastien Moret1, Scott Chadwick1, Chris Lennard2, Xanthe

Spindler1, Claude Roux1

1 Centre for Forensic Science, University of Technology Sydney, PO Box 123, Broadway, NSW 2007, Australia, 2 School of Science and Health, University of Western Sydney, Richmond, NSW 2753, Australia.

*Corresponding Author’s email; Mackenzie.delahunty@uts.edu.au

Title Page (with authors and addresses)

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INTERNAL USE Page 1

Highlights

Investigation into the chemical targets of physical developer

Induced sweating shows increased physical developer reactivity at pore locations

Physical developer eccrine reactivity requires the presence of non-water soluble

constituents

Physical developer may target a combination of eccrine and lipid constituents in fingermark

residue

*Highlights (for review)

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Understanding Physical Developer (PD): Part II – Is PD Targeting Eccrine Constituents?

Abstract

Physical developer (PD) is a fingermark development technique that deposits silver onto

fingermark ridges. It is the only technique currently in routine operational use that gives

results on porous substrates that have been wet. There is a reasonable understanding of the

working solution chemistry, but the chemical constituent(s) contained in fingermark residue

that are specifically targeted by PD are largely unknown. A better understanding of the PD

technique will permit a more informed selection of alternative or complementary detection

methods, and greater usage in operational laboratories. Recent research by our group has

shown that PD does not selectively target the lipids present in the residue.

This research investigated the hypothesis that PD targets the eccrine constituents in

fingermark residue. This was tested by comparison of PD and indanedione-zinc (Ind-Zn)

treated natural fingermarks that had been deposited successively, and marks that had been

deposited with a ten second interval in between depositions. Such an interval allows for the

regeneration of secretions from the pores located on the ridges of the fingers. On

fingermark depletions with no time interval between depositions, PD and Ind-Zn treated

depletions successively (and comparatively) decreased in development intensity as the

amount of residue diminished. Short time intervals in between successive depletions

resulted in additional secretions from the pores intermittently occurring, the increased

development of which was visualised by treatment with both PD and Ind-Zn. The changes in

development intensity were seen with both techniques on the same split depletions in a

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series, comparably and proportionately. These results indicate that the components

targeted by PD are contained in the material excreted by the friction ridge pores through its

mirrored development with Ind-Zn.

Repetition of the experiments on marks that only contained eccrine material showed good

Ind-Zn development but poor results with PD. This indicates that there are other

constituents contained in “natural” fingermarks that are required to be present for PD to be

able to target constituents in the eccrine sweat. It may be that the required constituents in

the natural residues are non-water soluble, and that these protect the eccrine constituents

from solubilisation in the aqueous washes employed in the PD method.

Further research is being undertaken to determine whether PD is targeting specific

compounds in the pore secretions, or a mixture of compounds consisting of the eccrine

material, epidermal lipids and sebaceous lipids typically present in latent fingermark

residues.

1. Introduction

The detection of latent fingermarks is an important area of forensic science. One technique,

physical developer (PD), is used to develop marks on porous surfaces that have been wet,

and is the only technique currently in routine use for this purpose by law enforcement

agencies [1]. PD is also used as a subsequent technique to other techniques used on porous

substrates such as ninhydrin, Ind-Zn and 1,8-diazafluoren-9-one (DFO) [2]. The PD working

solution selectively reduces silver ions in solution to metallic silver on the fingermark

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residue in an autocatalytic colloidal deposition process; however, the exact mechanism is

largely unknown. PD is an exceptionally unpredictable, expensive and difficult technique to

employ, due to the extremely contaminant-sensitive nature of the working solution. Some

of the issues encountered when using PD include adverse reactions to different paper types

[2], substrate damage from immersion of samples in the maleic acid prewash and

premature silver deposition from the working solution when using processing equipment

that has surface imperfections (scratches, dust etc.) [3]. While alternative techniques (Oil

red O, nile red) have been proposed, they have not been widely accepted into operational

use as they tend to behave differently to PD and thus cannot be classified as true

alternatives. True alternatives cannot be devised if the chemical targets of the technique

remain a mystery.

Residue found in the latent deposit of a fingermark is made up of a complex mixture of

constituents that can be divided into two major fractions; water soluble and water insoluble

[4]. The water soluble fraction is primarily made up of amino acids, proteins, urea and

inorganic salts, which originate in the eccrine glands and are excreted in eccrine sweat from

the pores on the fingers. An average person has more than two million functional glands on

the entire surface of the body, with the highest density on the volar surfaces of the fingers,

with an average of 530 glands·cm-2 and a water loss rate of 80-160 gh-1 [5]. The water

insoluble fraction is primarily made up of lipids, lipoproteins and insoluble proteins that

either originate in the epidermis and are contained in the hydrolipid film on the surface of

the skin (also known as acid mantle or skin surface lipids) or originate in the sebaceous

glands [6]. The sebaceous glands are only found in areas associated with hair growth and

not on the palms of the hands; therefore, constituents originating from the sebaceous

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glands are present in fingermark residue as a result of contact between the hand and these

areas of the body. Research has shown face-touching to be a frequent human behaviour

[7,8], explaining the continual identification of sebaceous components in fingermark residue

composition studies [9-12].

It has been observed that, in a latent fingermark deposit, the residue composition can vary

between the ridges and pore sites, supported by an understanding of the origin of the

constituents contained in fingermark residue. Sebaceous components are present along the

ridges of the finger, as a result of a physical transfer of material from other areas of the

body, whereas eccrine constituents are more concentrated around pore sites, from which

they are excreted. Different results between ridge and pore sites have been observed in

recent immunolabeling research [13, 14]. The observed development can either be strong

or completely absent at pore locations on the ridges, as the affinity of different antibodies

varied between the ridges and pore sites.

Recent research that evaluates non-water soluble constituents as the targets of PD

describes uniform silver deposition along the ridges of a PD-treated fingermark, and either

an absence of or an increase in silver deposition (when compared to the ridges) at pore sites

located along the ridges [15]. This variation indicates that the residue excreted from the

pores has a direct effect on the reactivity of the PD working solution with the fingermark

residue, supporting a hypothesis that PD may be targeting constituents in eccrine sweat

secreted by the pores.

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PD was previously thought to target the non-water soluble constituents contained within

the fingermark residue as such components would remain after water exposure. However,

recent work [15] has shown that PD does not specifically and/or solely target the lipids in

the residue. Spot tests of the major non-water soluble compounds found in fingermark

residue, treated with PD, showed that only cholesterol produced significant silver

deposition. PD is known to be effective on aged marks [16]; however, cholesterol degrades

over time [9] so PD reactivity towards fingermark residue cannot be solely attributed to the

presence of cholesterol. Samples that had been exposed to a variety of organic solvents

were also treated with PD and it was seen that, despite lipid removal by the solvents

(assessed by treatment with the lipid stain nile red), PD was effective in developing the

fingermarks. This indicated that PD is not solely targeting the lipids in the latent residue and

may be targeting constituents contained in eccrine sweat. The present research aims to

identify whether PD is instead targeting the water-soluble eccrine fraction of fingermark

residue through comparison of PD and Ind-Zn development at pore sites on the ridges of the

finger, using fingermark depletions.

2. Materials and Methods

Citric acid, maleic acid, zinc chloride, all solvents (analytical reagent grade) and silver nitrate

were obtained from BDH-Prolabo Chemicals (VWR International Pty. Ltd., Australia). Ferric

nitrate nonahydrate (Chem-Supply Pty Ltd, Australia), glacial acetic acid (Chem-Supply Pty

Ltd, Australia), 1,2-indanedione (Casali Institute, Israel), ammonium ferrous sulphate (Chem-

Supply Pty Ltd, Australia), n-dodecylamine acetate (Optimum technologies, Australia) and

Tween 20 surfactant (Sigma-Aldrich, USA) were used as supplied.

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2.1 Fingermark depletion deposition

Fingermark depletions are sequential impressions from the same finger to produce

increasingly weaker marks, and are recommend by the International Fingerprint Research

Group (IFRG) for assessing the sensitivity of fingermark development techniques [17]. In this

study, sequential impressions were used for a dual purpose; the first was to compare PD

and indanedione-zinc (Ind-Zn) on residue depleted marks, and the second was to observe

whether allowing time in between depletions encouraged additional excretions from the

pores on the fingers. Jasuja et al. [18] describe a correlation between the force applied

during deposition and the amount of residue that is deposited. They found that, regardless

of the amount of sweat present on the finger prior to deposition, the amount of material

deposited increased with increasing deposition force. Their results indicated that, despite

the initial sweat volume on the surface of the finger, if consistent force is applied during

deposition of the depletions then the same proportion of available secretions should be

transferred from the finger to the substrate. For this reason, the force applied during

deposition was carefully controlled throughout the experiment.

To investigate the hypothesis that PD may be targeting the eccrine constituent of latent

fingermark residue, PD was compared to Ind-Zn on split fingermark depletions. Two types of

depletion series were used; the first set was deposited successively with no time in between

depositions; the second set was deposited with a 10-second interval between successive

depletions to allow for pore excretion of eccrine fluids to naturally occur. The left half of the

depletions was developed in PD and the right half in Ind-Zn. Comparison of the results from

the two different depletion series was expected to allow for visualisation of successive

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decreases in PD and Ind-Zn development down the depletion series due to the decline in the

amount of residue present along the ridges, and possibly an increase in PD (if it is reactive

towards eccrine constituents) and Ind-Zn development at pore locations if ample pore

excretion time was allowed in between depositions.

In this study, fingermarks were deposited using a downward pressure that resulted in a

reading of 300 g on a laboratory balance and for a duration of 5 seconds in a depletion

series consisting of nine successive depositions. Natural and eccrine marks were obtained

for each different depletion type. Natural marks were obtained from two donors (one male

who was a good eccrine donor, poor sebaceous donor and one female who was a poor

eccrine donor, good sebaceous donor) who had not washed their hands within 1 hour of

fingermark collection. Marks containing only eccrine material (eccrine marks) were obtained

by thoroughly wiping the hands of one donor for 1 minute with an ethanol-soaked paper

towel. The hands were then placed in powder-free nitrile gloves for 30 minutes. Two

minutes after glove removal from both hands, fingermark depletions were deposited by one

hand either with or without a time interval between depositions, and then repeated with

the other. The experiment was performed in triplicate on 80 gsm Reflex Virgin Fibre

UltraWhite copy paper. After deposition, the samples were air dried for 48 hours in the dark

and then bisected vertically and developed. Visualisation of treated marks occurred within

12 hours of development to ensure optimal luminescence.

2.2 Physical developer formulation and application

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PD was prepared and applied as described previously by Ramotowski [19] with one major

deviation; the detergent solution was prepared by the addition of 1.5 mL Tween 20 and 1.5

g n-dodecylamine acetate into 1 L of deionised water, instead of the 3 mL and 3 g of,

respectively, Tween 20 and n-dodecylamine acetate recommended by Ramotowski. A 50 %

reduction in the concentration of surfactants leads to shorter development times. All

samples from the same depletion series were treated in the same PD working solution

concurrently to ensure consistent treatment time and an unbiased evaluation of

development intensity and contrast.

2.3 Indanedione-Zinc formulation and application

The Ind-Zn working solution was prepared by dissolving 0.60 g 1,2-indanedione-zinc in 90

mL ethyl acetate, 10 mL acetic acid and 900 mL of HFE 7100, and then adding 4 mL of a 4%

(w/v) ethanolic solution of zinc chloride with stirring. Samples were immersed in the reagent

for 2-3 seconds and allowed to air dry for 2 minutes. Ind-Zn treated samples were processed

in a dry heat press (Singer Magic Steam Press 7) at 155-160°C for 10 s [20]. All samples from

the same depletion series were treated in the same Ind-Zn working solution and heated in

the dry heat press concurrently to ensure consistent treatment time and an unbiased

evaluation of development intensity and contrast. The average relative humidity in the

laboratory during the experiments was 61%.

2.4 Sample visualisation

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PD-developed fingermarks were recorded using an Epson XP-200 A4 flatbed scanner using

2400 DPI resolution. Ind-Zn-developed fingermarks were visualised with a Polilight PL500

forensic light source coupled to a Rofin Poliview IV forensic imaging system (excitation 505

nm with a 555 nm band-pass barrier filter). All images were taken at the optimal exposure

for the first depletion in the series to show variations in luminescence intensity as the

depletion series progressed.

3. Results and Discussion

3.1 Fingermark depletions with no time interval between depositions

Natural and eccrine split fingermark depletions consisting of nine sequential depositions

were developed on the left side by PD and the right side by Ind-Zn (Table 1).

<INSERT TABLE 1>

3.1.1 Natural fingermark depletions

PD and Ind-Zn treated samples exhibit decreasing development quality as the amount of

fingermark residue depletes throughout the deposition series. These results were consistent

with each repetition of the experiment for each of the donors.

The PD-developed side of the depletion series varies in quality throughout the series.

Depletions 1–3 treated by PD show very strong development with full ridge details and are

identifiable fingermarks. The silver from the PD working solution has deposited relatively

uniformly along the length of the ridge. Depletions 4–6 show evidence of contact and some

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peripheral ridge development; however, the quality of development when compared to

depletions 1–3 has diminished significantly. Depletion 7 shows evidence of contact, but no

ridge development. Depletions 8 and 9 show little evidence of a fingermark.

The Ind-Zn-developed side of the depletion series is consistent through depletions 1–9. All

treated marks show continuous luminescent ridge development and are of identifiable

quality. Considering that all depletions were taken at the optimal exposure time for

depletion 1, a steady decrease in luminescence intensity can be seen throughout the series,

especially after the 1st depletion.

3.1.2 Eccrine fingermark depletions

PD was not sensitive enough to develop eccrine marks past the third depletion, whereas

Ind-Zn developed all marks in the series. The results show that the natural residue

contributes to PD reactivity on fingermarks, particularly residue depleted marks. This was

consistent for both donors in each repetition of the experiment.

The PD-developed side of the depletion series varies in development quality throughout the

series, but are in general of much lower quality compared to the natural secretions.

Depletion 1 is an identifiable mark that shows spotted and non-continuous ridge

development. The quality of depletion 2 is low, again showing a very spotted pattern.

Depletion 3 shows evidence of touch but with very weak contrast. Depletions 4–9 do not

show significant evidence of a fingermark being present.

The Ind-Zn marks are significantly more spotted in their development than for their natural

counterparts. Depletion 1 has minimal areas of continuous ridge detail. The developed spots

correspond to the locations of the pores on the fingers. Throughout the depletion series,

the development type varies between continuous ridge development and spotted

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development. The luminescence intensity slowly decreases from depletions 1 to 6 when

observing the central mark, but then increases slightly at depletion 7. The decrease is less

pronounced for the full marks, possibly a function of uneven force distribution during

deposition, or the lighting angle during sample visualisation. It is important to note that PD

development of depletions 1-3 was always present in the eccrine marks deposited by the

second hand after glove removal and was consistent with the repetitions of the experiments

with both donors. This is a result of the surface of the skin re-establishing a concentration of

surface skin lipids in the small time taken to deposit marks from the previous hand.

The results show PD and Ind-Zn to comparatively develop natural fingermark depletions,

with development quality decreasing throughout the depletion series as the amount of

residue decreases. Treated eccrine marks show Ind-Zn to be more effective than PD in the

development of residue depleted marks, indicating PD effectiveness is dependent on the

presence of constituents in the natural residue.

3.2 Fingermark depletions deposited with a ten second interval between sequential

depositions

<INSERT TABLE 2>

3.2.1 Natural fingermark depletions

It is clear that, over time, material is being excreted by the pores leading to sporadic

increases in development intensity, followed by decreases, and that this material is being

targeted by both development techniques. This is especially distinct in depletion 8 where

development by both techniques increases considerably from the previous depletion, and is

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extremely spotted in nature. This result was consistent for each repetition of the

experiment for each donor.

PD successfully developed all nine depletions; however, the development quality fluctuated

greatly. Depletion 1 shows a good, identifiable PD-developed mark with development

occurring continuously along the ridges, and then the same is seen in depletion 2 but with

less contrast. Depletion 3 shows a shift in the type of PD development from completely

detected ridges to development of material secreted by the pores on the ridges, giving very

spotted results, with much more contrast than for the development seen in depletion 2. In

terms of PD development, depletion 4 shows evidence of touch and some peripheral ridges,

but cannot be classified as an identifiable mark. Depletion 5 is better developed than

depletion 4, with mixed ridge and spotted development. Depletion 6 is more darkly

developed than the previous, with predominantly spotted development. Depletion 7

exhibits only slight development similarly to depletion 4. Depletion 8 shows good contrast,

but is extremely spotted with limited continuous ridge development. Depletion 9 shows a

lightly developed mark with significantly less detail than depletion 8. The extremely varied

development fluctuates in a cycle, representing the variable time taken for the pores to

excrete eccrine constituents.

Ind-Zn successfully developed all nine depletions with varying development quality and

type. In terms of Ind-Zn development depletions 1 and 2 are well-developed, identifiable

fingermarks that both have ridges featuring a lack of development at pore sites along the

ridge. This results in the appearance of undeveloped holes along the ridges. Depletion 3

shows a completely different result to that seen in depletions 1 and 2, featuring fully

developed ridges with no undeveloped areas along the ridge. The pore sites along the ridge

also feature increased development, resulting in the appearance of brightly luminescent

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spots along the developed ridges. Depletion 4 exhibits general ridge development with no

development at pore sites. Depletion 5 shows both ridge and spotted development.

Depletion 6 shows very spotted development that decreases slightly in depletion 7 but then

increases significantly in depletion 8. Depletion 9 decreases in luminescence intensity but

still exhibits spotted development.

3.2.2 Eccrine fingermark depletions

PD did not develop any of the eccrine marks, except for a small amount of spotted

development on depletion 6. As stated previously, eccrine marks deposited by the hand

immediately after glove removal, do not allow time for regeneration of compounds involved

in skin barrier function, as was the case here. This is evident in the lack of PD development

of these eccrine marks, supporting the idea that PD requires the presence of a combination

of constituents for the technique to be effective. Ind-Zn successfully developed all marks in

the depletion series. The developed eccrine marks are less spotted than the natural marks,

possibly due to the absence of hydrophobic lipids along the ridges that promote the

formation of sweat droplets at the pore openings. The lack of these lipids in the eccrine

marks may allow the sweat to spread along the ridges as it is excreted. This is supported by

the fact that all of the marks in the depletion series have a degree of continuous ridge

development, with none solely exhibiting spotted development. There is only slight

variation between the developed depletions, most notably in the amount of spotted

development combined with continuous ridge development, most notable in depletions 4,

5, 8 and 9.

The results indicate that the absence of certain constituents that are normally present in the

natural deposits produce fingermarks that cannot be effectively targeted by PD, but can still

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be developed by Ind-Zn. This implies that certain constituents contained in the natural

residue are needed to shield the eccrine constituents from solubilisation in the aqueous PD

washes, so they can be present and available for targeting by PD when immersed into the

PD working solution.

3.3 Types of development

Three types of development were identified in the experiments with both detection

techniques. The first was where development occurred along the length of the fingermark

ridge but was absent at pore sites. The second type was where development occurred along

the length of the fingermark ridge and was increased at the pore sites. The third type of

development was where there was only development at the pore sites, with no

development along the length of the fingermark ridge, giving spotted development. These

different development types are caused by variations in residue composition and

constituent concentration and location on the finger at the time of deposition [13, 14, 21].

It is expected that the material concentrated around the pore sites would be mostly

comprised of eccrine gland originating constituents, and the residue along the ridges of the

fingers would predominantly contain endogenous surface skin lipids, some eccrine material

that has spread across the ridges of the finger and some sebaceous gland originating

constituents present as a result of touching particular areas of the body. This would explain

why there are two areas of differing development (the pore sites and the ridges).

3.4 Effect of a time interval between successive depositions

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The time interval in between depositions significantly affected PD effectiveness on the

natural marks. When no time interval was allowed between depositions, the fingermarks

were sequentially depleted in development quality as the amount of residue lessened

throughout the series, as also observed by Attard-Montalto et al. [22]. When a time interval

was allowed between sequential depositions, spotted development was observed as a

result of development of the constituents excreted by the pores on the finger. The time

interval demonstrates the selectivity and specificity of PD to constituents contained within

eccrine sweat. This is affirmed by the mirrored increases and decreases in development of

pore secretions by Ind-Zn and PD on the same depletions.

3.5 Potential targets of PD in latent fingermark residue

The comparable and proportional increases and decreases in PD and Ind-Zn development of

the natural fingermark depletions suggests that both techniques are targeting components

of the residue excreted by the pores. This is an expected result for Ind-Zn, as it targets the

amino acids contained in eccrine sweat; however, this is surprising for PD. Considering that

the results obtained in the first study [15] indicated that PD is not specifically targeting the

lipids, and the results of this study indicate that PD has an affinity for the eccrine material, it

would be logical to conclude that PD is not targeting the lipids and is targeting the eccrine

material. However, most of the constituents contained within the eccrine sweat are water

soluble, and thus would be removed by water exposure and could not be targets for PD.

This suggests that, if the eccrine constituent of fingermark residue is actually the specific

target of PD then, for it to remain on a substrate after water exposure, the lipids must either

be intimately mixed with it or form a protective layer to avoid solubilisation. The results

obtained using eccrine marks support this hypothesis as the lack of consistent PD

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development in both eccrine depletion series indicates that PD is targeting the eccrine

material but, in order for the eccrine material to remain present when exposed to water, it

needs to be in a mixture with non-water soluble (lipid) material. The development of the

first three depositions in eccrine depletions only occurred when a few minutes was allowed

between glove removal and fingermark deposition, as the surface skin lipids have begun to

regenerate (gloves were removed from both hands at the same time, and then depletions

were deposited one hand at a time). The second hand to deposit marks consistently saw PD

develop the first three depletions in the series with both donors.

The results obtained in this study suggest that the chemical target(s) of PD are contained in

the eccrine sweat but that these can only be targeted in the presence of other chemical

constituents contained in natural fingermark residue. These constituents are most likely

non-water soluble compounds that act as a protectant from water solubilisation of the

targeted compounds, explaining why PD works on fingermarks that have been wet or

exposed to high humidity. It is clear that the presence of both non-water soluble

constituents from the skin surface and eccrine constituents (predominantly water soluble)

excreted by the pores is required for PD reactivity and selectivity. It is not yet known

whether PD reactivity is dependent on a particular concentration or ratio of these different

constituents, or on their method of integration (if any) either in a liquid phase shortly after

deposition or through the substrate over time, or whether the phases in which these

constituents exist, either individually or in combination, have an effect on PD development.

The results obtained in this study have provided us with important information as to the

potential targets of PD being in a mixture of compounds, containing eccrine material.

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Further research is being undertaken by our group to investigate the targets of PD as a

means of obtaining a better understanding of the technique.

4. Conclusions

PD is a sensitive fingermark detection technique and is the only one in current routine

operational use by forensic laboratories for the treatment of porous surfaces that have been

wet. The mechanism by which it develops fingermarks remains largely unknown, making it

difficult for the technique to be improved or alternative techniques suggested. The aim of

this research was to provide some insight into the chemical targets of PD contained within

the latent fingermark residue. Three hypotheses have been proposed by our research group

as to the targets of the technique:

1. PD is targeting the lipids contained in the residue that can either originate in the

epidermis or are present from face touching and originate in the sebaceous glands;

2. PD is targeting eccrine constituents secreted by the pores on the friction ridge skin of the

hands;

3. PD is targeting a defined mixture of lipid and eccrine constituents, both of which must be

present for silver deposition to selectively occur on latent fingermark deposits.

Previous work by our group showed that PD does not selectively deposit silver onto a

selection of lipids found in either the epidermis or in the sebaceous gland secretions [15].

The research presented here shows PD to be selective to the residue that is secreted by the

pores on the fingers, through comparison of PD development with Ind-Zn development. An

increase in development by both PD and Ind-Zn at the pore sites showed that PD is reactive

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towards the eccrine sweat excreted by the pores on the fingers, the same fraction targeted

by the amino acid sensitive Ind-Zn. The development by Ind-Zn, in conjunction with the lack

of development by PD on marks than only contained eccrine material (through physical

removal of the lipids with ethanol), showed that certain constituents contained in natural

fingermark residue need to be present for PD to selectively target the eccrine sweat. This

suggests that PD may be targeting eccrine material, which is protected from solubilisation

during water exposure by non-water soluble constituents found in natural fingermark

residue.

Further research is needed to identify the specific targets and the conditions required for

their PD development, as well as the state in which these targets are present, that is, as a

mixture of various compounds or as an emulsion. Our research group is currently

investigating these two possibilities.

5. References

1. Ramotowski, R., Lipid Reagents, in Lee and Gaensslen's Advances in Fingerprint Technology, Third Edition. 2012, CRC Press. p. 83-96.

2. Marriott, C., Lee, R., Wilkes, Z., Comber, B., Spindler, X., Roux, C., and Lennard, C., Evaluation of fingermark detection sequences on paper substrates. Forensic Science International, 2014. 236: p. 30-37.

3. Home Office, Fingermark Visualisation Manual First Edition. 2014, Centre for Applied Science and Technology: United Kingdom.

4. Cantu, A.A., Silver physical developers for the visualisation of latent prints on paper. Forensic Science Review, 2001. 13: p. 30-64.

5. Taylor, N. and Machado-Moreira, C., Regional variations in transepidermal water loss, eccrine sweat gland density, sweat secretion rates and electrolyte composition in resting and exercising humans. Extreme Physiology & Medicine, 2013. 2: p. 4-4.

6. Ramotowski, R., Composition of Latent Print Residue, in Advances in Fingerprint Technology, Second Edition. 2001, CRC Press.

7. Dimond, S. and Harries, R., Face touching in monkeys, apes and man: Evolutionary origins and cerebral asymmetry. Neuropsychologia, 1984. 22: p. 227-233.

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8. Hatta, T. and Dimond, S.J., Differences in face touching by Japanese and British people. Neuropsychologia, 1984. 22: p. 531-534.

9. Archer, N.E., Charles, Y., Elliott, J.A., and Jickells, S., Changes in the lipid composition of latent fingerprint residue with time after deposition on a surface. Forensic Science International, 2005. 154: p. 224-239.

10. Croxton, R.S., Baron, M.G., Butler, D., Kent, T., and Sears, V.G., Variation in amino acid and lipid composition of latent fingerprints. Forensic Science International, 2010. 199: p. 93-102.

11. Girod, A., Ramotowski, R., and Weyermann, C., Composition of fingermark residue: A qualitative and quantitative review. Forensic Science International, 2012. 223: p. 10-24.

12. Girod, A. and Weyermann, C., Lipid composition of fingermark residue and donor classification using GC/MS. Forensic Science International, 2014. 238: p. 68-82.

13. van Dam, A., Aalders, M., van de Braak, K., Hardy, H., van Leeuwen, T., and Lambrechts, S., Simultaneous labeling of multiple components in a single fingermark. Forensic Science International, 2013. 232: p. 173-179.

14. Drapel, V., Becue, A., Champod, C., and Margot, P., Identification of promising antigenic components in latent fingermark residues. Forensic Science International, 2009. 184: p. 47-53.

15. de la Hunty, M., Moret, S., Chadwick, S., Lennard, C., Spindler, X., and Roux, C., Understanding Physical Developer (PD): Part I – Is PD Targeting Lipids? . Forensic Sci Int, 2015. doi: 10.1016/j.forsciint.2015.06.034

16. Anon., What is the oldest fingerprint that you have developed?, in Fingerprint Development and Imaging Update. Publication No. 26/2003. 2003, Home Office Police Scientific Development Branch.

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18. Jasuja, O.P., Toofany, M.A., Singh, G., and Sodhi, G.S., Dynamics of latent fingerprints: The effect of physical factors on quality of ninhydrin developed prints — A preliminary study. Science & Justice, 2009. 49: p. 8-11.

19. Ramotowski, R., Metal Deposition Methods, in Lee and Gaensslen's Advances in Fingerprint Technology, Third Edition. 2012, CRC Press. p. 55-82.

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22. Attard-Montalto, N., Ojeda, J., Reynolds, A., Ismail, M., Bailey, M., Doodkorte, L., de Puit, M., and Jones, B., Determining the chronology of deposition of natural fingermarks and inks on paper using secondary ion mass spectrometry. Analyst, 2014. 139: p. 4641-4653.

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Table 1: PD treated samples (left image) visualised by high resolution scanning of samples on an Epson scanner and Ind-Zn treated samples (right image) visualised with a Polilight PL500 forensic light source coupled to a Rofin Poliview IV forensic image capturing and enhancement system (excitation 505 nm with a 555 nm band-pass barrier filter). Natural (left column) and eccrine (right column) fingermark depletions were obtained with no time interval between depositions

Depletion Natural fingermarks Eccrine fingermarks

1

2

3

4

5

Table 1

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Table 1: PD treated samples (left image) visualised by high resolution scanning of samples on an Epson scanner and Ind-Zn treated samples (right image) visualised with a Polilight PL500 forensic light source coupled to a Rofin Poliview IV forensic image capturing and enhancement system (excitation 505 nm with a 555 nm band-pass barrier filter). Natural (left columns) and eccrine (right columns) fingermark depletions were obtained with a 10 second time interval between depositions

Depletion Natural Marks Eccrine marks

1

2

3

4

5

Table 2

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