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Monday, November 17, 2008

The purpose of the Detail is to help keep you informed of the current state of affairs in the latent print community, to provide an avenue to circulate original fingerprint-related articles, and to announce important events as they happen in our field.
Breaking NEWz you can UzE...
by Kasey Wertheim
SBI agents: DNA, footprints at murder scene belong to Hartley
Sampson Independent, NC - Nov 14, 2008
“I was able to identify the latent fingerprint on the piece of tape as the left index finger of Kenneth Mark Hartley,” she said. The next to give testimony ...
Juror ExplainsVerdict [of Not-Guilty] In Double Murder
WSMV, TN - Nov 13, 2008
Prosecutors tried to show he was there, connecting him with a bloody fingerprint and DNA. ...
New Purdue-developed forensics tool gains national attention
The Exponent, IN - Nov 12, 2008
"Can DESI characterize latent fingerprints? Absolutely. Can it do it fast enough and cheaply enough to be of value in a forensic lab right now? No way...
UK fingerprint 'developer' can read a letter from its envelope, VA - Nov 10, 2008
Paul Kelly and colleagues at Loughborough University found that a disulfur dinitride (S 2 N 2 ) polymer turned exposed fingerprints brown, as the polymer ...

Recent CLPEX Posting Activity
Last Week's Board topics containing new posts
Moderated by Steve Everist and Charlie Parker

Public CLPEX Message Board
Moderated by Steve Everist

by atodd on Fri Nov 14, 2008 11:58 am 2 Replies 70 Views Last post by George Reis
on Sun Nov 16, 2008 2:43 pm

Certification question
1, 2by R.H. on Sat Nov 08, 2008 4:03 pm 19 Replies 567 Views Last post by Charles Parker
on Sun Nov 16, 2008 10:58 am

Case at Supreme Court
1, 2by Pat A. Wertheim on Mon Mar 17, 2008 5:01 pm 16 Replies 2303 Views Last post by L.J.Steele
on Fri Nov 14, 2008 8:34 pm

News Article: Slaying Arrest a Result of Mistaken ID
by Steve Everist on Fri Nov 14, 2008 3:12 pm 0 Replies 72 Views Last post by Steve Everist
on Fri Nov 14, 2008 3:12 pm

by Boyd Baumgartner on Fri Nov 14, 2008 11:44 am 0 Replies 84 Views Last post by Boyd Baumgartner
on Fri Nov 14, 2008 11:44 am

HDR Latent/Evidence Photography
by Boyd Baumgartner on Thu Oct 02, 2008 2:02 pm 5 Replies 396 Views Last post by Gerald Clough
on Fri Nov 14, 2008 11:01 am

Tribunal for McKie print expert
1, 2, 3by charlton97 on Thu Sep 11, 2008 1:00 am 42 Replies 2762 Views Last post by Iain McKie
on Thu Nov 13, 2008 6:24 pm

Footwear outsole dust impressions
by Jan Seaman Kelly on Mon Nov 10, 2008 5:19 pm 2 Replies 127 Views Last post by Jan Seaman Kelly
on Thu Nov 13, 2008 5:27 pm

Hot Sauce for Difficult Record Prints
by Ernie Hamm on Thu Nov 13, 2008 10:13 am 1 Replies 126 Views Last post by Ernie Hamm
on Thu Nov 13, 2008 5:03 pm

Latent Print Exam and Forensic Tech Positions - CONUS/OCONUS
by wkpetroka on Tue Apr 15, 2008 1:31 pm 1 Replies 1380 Views Last post by wkpetroka
on Wed Nov 12, 2008 11:22 am

Permanence of 3rd level detail??
1, 2by antonroland on Mon Jul 14, 2008 4:45 am 29 Replies 1667 Views Last post by Les Bush
on Tue Nov 11, 2008 5:15 pm

Fingerprinting merit badge
by L.J.Steele on Mon Nov 10, 2008 8:41 am 4 Replies 169 Views Last post by Gerald Clough
on Mon Nov 10, 2008 5:12 pm

Evidence Fabrication in South Africa
1 ... 19, 20, 21by Pat A. Wertheim on Fri Nov 30, 2007 12:48 pm 308 Replies 35151 Views Last post by WRoughead
on Mon Nov 10, 2008 10:29 am

Training Classes in Austin
by Charles Parker on Mon Nov 10, 2008 8:22 am 0 Replies 96 Views Last post by Charles Parker
on Mon Nov 10, 2008 8:22 am

AFIS Suitability
by Charles Parker on Sun Nov 09, 2008 9:46 am 6 Replies 205 Views Last post by Bill Schade
on Sun Nov 09, 2008 9:29 pm

IAI Conference Topics -
Louisville, Kentucky 2008:
Moderator: Steve Everist

No new posts

Documentation issues as they apply to latent prints
Moderator: Charles Parker

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Historical topics related to latent print examination
Moderator: Charles Parker

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Updated the Fingerprint Interest Group (FIG) page with FIG #70; a really neat example of a Small Temporary Injury resulting in apparent ridge features, by J. Flanders of Texas.  You can send your example of unique distortion to Charlie Parker:  For discussion, visit the forum FIG thread.

Updated the forum Keeping Examiners Prepared for Testimony (KEPT) thread with KEPT #44; Certification - Do you have to be certified?; submitted by Michelle Triplett.  You can send your questions on courtroom topics to Michelle Triplett:

Updated the Detail Archives

Last week

we looked at an editorial advocating that multi-modal identification will reduce the reliance on fingerprint AFIS systems.

This week

we look at a new fingerprint technique discovered by Paul F. Kelly and Colleagues at Loughborough University in the UK:

Fingerprint and Inkjet-Trace Imaging Using Disulfur Dinitride

by Paul F. Kelly*, Roberto S. P. King and Roger J. Mortimer
Department of Chemistry, Loughborough University, Leics, UK

Received (in Cambridge, UK) 9th September 2008,
Accepted 2nd October 2008
First published on the web 17th October 2008
Chemical Communications (Chem. Commun.), 2008DOI: 10.1039/b815742a

Some three decades ago, the discovery of the fascinating conductivity properties of (SN)x stimulated much interest in both the polymer itself and in its precursor, the four-membered square molecule S2N2.1 Interest in both species continues to this day; thus recent work has, for example, probed the structure of both the monomer2 and of the polymer,3 and investigated the polymerisation process.4 Work in our group has looked at polymerisation within the confinement of a zeolitic system5 and at preparation of selenium analogues.6 For all this interest, however, and despite the intensity of the initial work prompted by the first observations of superconductivity,7 practical applications of the polymerisation process, and utilisation of the polymer, have largely remained elusive. Although some success at incorporating the polymer into functional systems has been recorded (see examples quoted in ref. 1), the efficiency and stability of such arrangements appears to have mitigated against realistic applications. Here we report an unexpected observation regarding the interaction of S2N2 with forensically pertinent materials, and show that polymerisation may be induced and visualisation of the material effected through the resulting dark blue/black polymer.

Disulfur dinitride, S2N2, can be generated by the thermal cracking of S4N4 through silver wool, and in the course of previous work on loading this material into zeolite cavities, we reported a modified apparatus that allowed its production efficiently and safely.5 The latter reactions were brought about by introducing the zeolite into vacuum systems containing S2N2, the volatile nature of the latter then meaning that simply warming the system to ambient temperature under reduced pressure allowed the nitride to diffuse into the samples. During the course of such work it became apparent that the nitride interacted with fingerprints that were randomly present on sample vials containing the zeolite samples. This serendipitous observation lead to a more systematic evaluation of this process.

Samples containing fingerprints on a range of media were introduced to S2N2 atmospheres using the same reaction vessels previously employed in the zeolite work.5 Fig. 1 illustrates examples of prints obtained from six different media, chosen to represent as wide a variety of porosity, chemical composition and morphology as possible. In all cases it is apparent that interaction of S2N2 with the fingerprints has induced polymerisation, which has then progressed with time (typical exposure time was 2–3 h), eventually imaging the print. It is important to note a number of points about this effect. Firstly, the materials in question were not primed or cleaned in any way—simply used as received. Secondly, prints placed on the materials were not deliberately charged with excess secretions by deliberate loading, they were merely performed as straightforward thumb prints, from a number of individuals, in a manner consistent with the everyday deposition of prints pertinent to forensic application. Finally, because the polymer is a dark blue/black colour, all the prints shown are immediately apparent to the naked eye—those in Fig. 1 have simply been photographed (with magnification in the case of the paper sample, to give an indication of the level of resolution achieved) and the colour removed.

Fig. 1 The induced growth of (SN)x over latent fingermark residues on various sample surfaces (Clockwise from top left: paper, pottery, aluminium foil, clingfilm, glass, cotton).

The presence of the polymer in the developed prints is strongly hinted at by the colour of the material (dark blue/black, though golden in strong reflected light) as there are few chromophores of this nature within sulfur–nitrogen chemistry.8 It can be confirmed, though, by the use of Raman microscopy (Fig. 2). The developed prints appear air stable, for many days (at least) and, if anything, are even more stable to aerial hydrolysis than bulk samples of the pure polymer. All samples are indefinitely stable under an inert atmosphere, however. The nature of the initial interaction between the S2N2 and the materials present in the print has yet to be fully elucidated. Interestingly, prints can be obtained from paper which (after placement of the fingerprint) has been soaked under water or under ether, and then dried. Different components of the print would be expected to be removed in each case, but either residue appears to still be amenable to this technique, suggesting that more than one class of component can interact with the nitride.

Fig. 2 Comparison of the Raman spectrum of (SN)x (lower) with that grown on the latent fingermarks (upper), obtained through in situ Raman microscopy.

In light of the above success, the interaction of S2N2 with other substrates was investigated. One of these was inkjet ink, the assumption being that it might act as a nucleation site for polymer growth, and indeed preliminary results indicated that the latter did indeed form around the small amount of ink present in washed out images.9 In fact, subsequent work revealed that S2N2 is exceptionally sensitive to components of this ink, so much so that invisible traces left by direct contact can be enhanced. This is illustrated in Fig. 3; here, text has been printed, allowed to dry and then placed in an envelope. This was left overnight (with a small book placed on the envelope to ensure constant contact) and then the envelope opened, the contents removed, and the patch of envelope that had been in contact with the print was cut out. At this stage this area appeared completely blank; upon exposure to S2N2, however, the text transferred from printed paper to envelope, via the small amount of ink diffusion, is developed. Upon being removed from the vacuum apparatus and photographed the presence of text is clearly visible (in, of course, a mirror image).

Fig. 3 Close-up of the image obtained when a sample area (ca. 1 width) from the inside of an envelope, which had been in contact with 12-point inkjet text, was exposed to S2N2. Note that before exposure the area appeared completely blank and that the above is the raw image, with no processing to the original digital photograph, save colour removal from the paper. Of course this is a mirror image of the original text; subsequent digital processing can correct this, and further resolve the text via simple contrast enhancement.

The interaction of S2N2 with traces of inkjet components is so sensitive that the minute amounts diffusing through an entire sheet of paper can be detected. Thus, in Fig. 4, an image was printed and placed in an envelope; a sheet of paper was placed onto the envelope and the combination weighted to keep the components in place. After a number of days the external sheet was removed and the area adjacent to the image within the envelope cut out and exposed to S2N2 in the usual manner. Although rather poorly resolved, the image from inside the envelope is nevertheless clearly visible (in this case the image has been contrast enhanced).

Fig. 4 (left) Original image printed out in inkjet and then placed in an envelope; (right) image (contrast enhanced) obtained without opening the envelope, via enhancement (using S2N2) of the minute amount of inkjet diffusing through the envelope and on to an external sheet of paper (n.b. the mirror image is shown here for easier comparison with the original).

This result clearly indicates that initial interaction of S2N2 with a component of the inkjet ink can be initiated at extremely small quantities of the latter; presumably then further crystallisation of the polymer occurs over this initial product, and thus the image is built up. This diffusion experiment also shows that it must be a liquid component of the ink that is responsible for the effect. Direct contact of printed paper to blank sheets could transfer small amounts of solid material which could, conceivably, act as nucleation sites for polymer growth. However, this could not produce results such as those illustrated in Fig. 4. Thus it is some mobile component of the ink which is responsible, and future work will attempt to determine the nature of this component.

The results with fingerprints and with inkjet clearly highlight and unexpected forensic promise associated with the S2N2/(SN)x system. This is particularly true in the fingerprints case as, despite the long history of print analysis, there is still a keen and active interest in the development of new techniques for latent fingermark enhancement/imaging.11–17 Of all types of fingermark evidence, the latent print is not only the most commonplace, but also the most difficult to detect since they are largely invisible and typically require either chemical (ninhydrin, DFO, etc.), optical (luminescence, UV, etc.), or physical (powdering, vacuum metal deposition (VMD), multi-metal deposition (MMD), etc.) treatment to differentiate them from the substrate material to which they are bound. Unfortunately, due to the ever increasing array of surface types and materials (porous, non-porous, semi-porous, textured, recycled etc.) many detection techniques are effective on some substrates, but not others. Often, therefore, multi-step sequencing of detection techniques is essential for optimised clarity of results.18 Intriguingly, it appears that (SN)x growth across fingermark residues is not affected by surface type. We have shown good detection is possible on both porous, semi-porous and non-porous substrates. Common problematic samples, such as aluminium, cotton (Fig. 1) and detonated cartridge shells (Fig. 5) (where the heat generated through firing can deplete/disrupt fingermarks on the shell casing) have all provided positive results.

Fig. 5 Fingerprints (deposited before firing) developing on a spent blank gun cartridge, photographed in situ during exposure to S2N2.

The use of an inexpensive, non destructive, solvent free, self imaging material could be considered the ideal technique for latent fingerprint detection; especially if its use could be extended to various surface types. In many ways S2N2 fits the bill very effectively, thanks to the versatility of the media upon which prints can be developed, the fact that clearly visible images are generated, the fact that exposure times are quite low (prints start to develop within minutes of exposure) and that it is non destructive and non solvent based. Clearly there are limitations to the technique, thanks to the fact that the apparatus required for the generation of S2N2 would, in its current guise, preclude portability; in addition, care is required in the handling of the S4N4 starting material. That said, the continued requirement for new fingerprint imaging methods means that the versatility of the technique could make it viable, alongside other vacuum deposition techniques currently in practice. When the unusual results with inkjet interactions are also considered, it is clear that the venerable S2N2/(SN)x system still has plenty of potential to surprise us.

We are grateful to Prof. Derek Woollins, University of St.Andrews, for very helpful advice on S2N2 generation and to John Spray, Loughborough University, for the preparation of the custom apparatus used to achieve this. We are endebted to Dr Helen Reid of Loughborough University for very helpful discussions during the early stages of this work.

Notes and references

1 For an overview of (SN)x and properties see: A. J. Banister and I. B. Gorrell, Adv. Mater., 1998, 10, 1415 [Links].
2 H. M. Tuononen, R. Suontamo, J. Valkonen, R. S. Laitinen and T. Chivers, J. Phys. Chem. A, 2005, 109, 6309 [Links].
3 R. C. Mawhinney and J. D. Goddard, THEOCHEM, 2008, 856, 16 [Links].
4 (a) H. Müller, S. O. Svensson, J. Birch and Å. Kvick, Inorg. Chem., 1997, 36, 1488 [Links]; (b) R. C. Mawhinney and J. D. Goddard, Inorg. Chem., 2003, 42, 6323 [Links].
5 R. S. P. King, P. F. Kelly, S. E. Dann and R. J. Mortimer, Chem. Commun., 2007, 4812 [Links].
6 S. M. Aucott, D. Drennan, S. L. M. James, P. F. Kelly and A. M. Z. Slawin, Chem. Commun., 2007, 3054 [Links].
7 M. M. Labes, P. Love and L. F. Nichols, Chem. Rev., 1979, 79, 1 [Links].
8 See T. Chivers, A Guide to Chalcogen-Nitrogen Chemistry, World Scientific Publishing, Hackensack NJ, 2004. An exception is the (S4N)− anion which is intensely dark blue.
9 .
10 J. D. Woollins, Polyhedron, 1987, 6, 939 [Links].
11 M. Zhang, A. Becue, M. Prudent, C. Champod and H. H. Girault, Chem. Commun., 2007, 3948 [Links].
12 R. Jelly, S. W. Lewis, C. Lennard, K. F. Lim and J. Almog, Chem. Commun., 2008, 3513 [Links].
13 D. B. Hansen and M. M. Joullie, Chem. Soc. Rev., 2005, 34, 408 [Links].
14 S. Morimoto, A. Kaminogo and T. Hirano, Forensic Sci. Int., 1998, 97, 101 [Links].
15 G. S. Sodhi and J. Kaur, Forensic Sci. Int., 2001, 115, 69 [Links].
16 G. S. Sodhi and J. Kaur, Forensic Sci. Int., 2001, 120, 172 [Links].
17 S. M. Bleay, G. Bradshaw and J. E. Moore, HOSDB Newsletter 26/06, 2006.
18 For an overview of fingerprints and detection techniques, see both C. Champod, C. Lennard, P. Margot and M. Stoilovic, Fingerprints and Other Ridge Skin Impressions, ed. T. Kent, CRC Press, 2004, Manual of Fingerprint Development Techniques 2nd Edition, PSDB, 1998 (updated 2002 and 2005).

Safety note! In the pure form both S4N4 and S2N2 are friction sensitive. For fingerprint detection attempts, all sample surfaces were contaminated with fingermarks from various individuals. For ink transfer detection attempts, images/script were printed onto paper (Epson Stylus Photo R26 inkjet printer)), allowed to dry and then placed in contact with the appropriate media. Contact between the two surfaces was initially ensured through use of a paperweight. In such cases all contact surfaces were visibly image free prior to S2N2 exposure.Preparation of S2N2 and exposure to materials.S2N2 was prepared using a modification of the traditional route (the cracking of S4N4 vapour over heated silver wool),10 using a tailored, compact variation on the previous apparatus, as described previously,5 and the target sample(s) (fingerprint or ink contaminated) were placed in the sidearm. Upon warming, the volatile S2N2 was then able to diffuse over the target sample. In the case of fingerprints, a faint red colouration was noted along the ridges of the print within just a few minutes of exposure. Further exposure for ca. 2–3 h allowed for full development of the image as dark blue/black polymer. In the case of inkjet traces, a longer exposure time was required, with samples typically left overnight under the vacuum/S2N2 atmosphere.


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KEPT - Keeping Examiners Prepared for Testimony - #44
by Michele Triplett, King County Sheriff's Office


Disclaimer:  The intent of this is to provide thought provoking discussion.  No claims of accuracy exist. 


Question – Certification:

Do you have to be certified?


Possible Answers:

a)      No

b)      No, my agency doesn’t require certification but they do require that I pass yearly proficiency tests.

c)      Yes, we have to be certified by the state patrol to use the AFIS computer system.

d)     No, my agency doesn’t require it but I am certified by the International Association of Identification.

e)      Yes, it’s a requirement of my agency to be certified by the International Association for Identification.



Certification adds weight and credibility to an examiners value as an expert by showing that the examiner has a certain knowledge level and competency level.  It shows that an examiner is professional and has access to current information.

a and b)  If an agency doesn’t require an expert to be certified then this is the correct answer but an examiner may want to add more information, as with answer b, so it doesn’t sound like the agency has poor standards.

c) This answer is slightly misleading because most people think of certification as being from the IAI and not strictly for the AFIS computer usage.  If an examiner works for an area that has multiple certification programs then the examiner should ask for clarification prior to answering the question.

d) Even if an agency doesn’t require certification, examiners may want to consider getting certified on their own.  Being certified prevents many other questions about examiners qualifications from being asked in court.

e) Many agencies are now requiring certification.  If you are considering taking the test, a good practice exam for the knowledge portion of the test was made by Henry Templeton and can be found at:




Feel free to pass The Detail along to other examiners.  This is a free newsletter FOR latent print examiners, BY latent print examiners. With the exception of weeks such as this week, there are no copyrights on The Detail content.  As always, the website is open for all to visit! 


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Until next Monday morning, don't work too hard or too little.

Have a GREAT week!