Breaking NEWz you can UzE...
Recent CLPEX Posting Activity
containing new posts
Moderated by Steve Everist and Charlie Parker
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
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
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
No new posts
Historical topics related to latent print examination
Moderator: Charles Parker
No new posts
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
For discussion, visit the CLPEX.com forum FIG thread.
Updated the forum Keeping Examiners Prepared for
thread with KEPT #44; Certification - Do you have to be certified?;
by Michelle Triplett. You can send your
questions on courtroom topics to Michelle Triplett:
Updated the Detail Archives
we looked at an editorial advocating that multi-modal
identification will reduce the reliance on fingerprint AFIS systems.
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
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
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
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
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
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
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 http://www.rsc.org/chemistryworld/News/2007/July/13070701.asp .
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
14 S. Morimoto, A. Kaminogo and T. Hirano, Forensic Sci. Int., 1998, 97,
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,
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
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.
This journal is © The Royal Society of Chemistry 2008
All rights reserved by the copyright holder. No part of this
publication may be reproduced or transmitted, in any form or by any
means, electronic, mechanical, photocopying, recording or otherwise, or
be stored in any retrieval system of any nature, without written
permission of the copyright holder and the Publisher, application for
which shall be made to the publisher. www.clpex.com makes such material
available in an effort to advance scientific understanding in the field
of latent prints, thus constituting a 'fair use' of any such copyrighted
material as provided for in section 107 of the US Copyright Law. In
accordance with Title 17 U.S.C. Section 107, the material on this site
is displayed without profit to those who wish to view this information
for research and/or educational purposes. If you wish to use
copyrighted material from this site for purposes of your own that go
beyond 'fair use', you must obtain permission from the copyright owner.
- Keeping Examiners Prepared for Testimony - #44
by Michele Triplett, King County
Disclaimer: The intent of this is to
provide thought provoking discussion. No claims of accuracy exist.
Question – Certification:
Do you have to be certified?
No, my agency doesn’t require certification but they do
require that I pass yearly proficiency tests.
Yes, we have to be certified by the state patrol to use the
AFIS computer system.
No, my agency doesn’t require it but I am certified by the
International Association of Identification.
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!
If you have not yet signed up to receive the
Weekly Detail in YOUR e-mail inbox, go ahead and
join the list now so you don't miss out! (To join this free e-mail
newsletter, enter your name and e-mail address on the following page:
You will be sent a Confirmation e-mail... just click on the link in that
e-mail, or paste it into an Internet Explorer address bar, and you are
signed up!) If you have problems receiving the Detail from a work
e-mail address, there have been past issues with department e-mail filters
considering the Detail as potential unsolicited e-mail. Try
subscribing from a home e-mail address or contact your IT department to
allow e-mails from Topica. Members may unsubscribe at any time.
If you have difficulties with the sign-up process or have been inadvertently
removed from the list, e-mail me personally at
email@example.com and I will try
to work things out.
Until next Monday morning, don't work too hard or too little.
Have a GREAT week!