Bulletproof fingerprint technology takes images in the round

Date:
November 15, 2021
Source:
University of Nottingham
Summary:
Experts have developed a unique method for retrieving high
resolution images of fingermarks from curved objects like bullet
casings that offers greater detail and accuracy than traditional
forensic methods.



FULL STORY ========================================================================== Experts have developed a unique method for retrieving high resolution
images of fingermarks from curved objects like bullet casings that offers greater detail and accuracy than traditional forensic methods.


========================================================================== Scientists from the University of Nottingham developed a rotation stage to allow researchers and forensic practitioners to perform highly sensitive,
non- destructive Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS) measurements and develop high resolution fingerprint images on surfaces
that conventional fingerprint imaging fails to pick up at all. The
rotation stage that they have developed opens up new possibilities for
the retrieval of high- resolution fingerprints from the whole surface
area of challenging shapes and materials like metal bullet casings.

Retrieval of fingermark evidence from bullet casings is an area of
major difficulty for forensic scientists. While both fired and unfired
casings can often be found at the scene of violent crimes, retrieving fingermarks and linking the person that loaded the gun to the crime has consistently proven to be difficult because of the physical conditions
that are experienced by the bullet casings during firing and techniques
that are used to develop and image the fingermarks.

When a bullet is fired, the casing experiences high temperatures,
pressures and large friction forces inside the barrel of the gun. They
can also be coated by the residues of propellant and the powder that
are used to generate the reaction that forces the bullet out of the
chamber. These combined effects often result in the removal, evaporation
or degradation of the more volatile components of fingermark residue (such
as water, amino acids and low molecular weight organics such as lipids),
as well as potential smudging or obscuring the mark. These factors can
make it difficult for conventional methods of fingermark retrieval such
as cyanoacrylate (superglue) fuming and fluorescent staining approaches
to work.

ToF-SIMS is a sensitive surface-analysis technique that provides very
detailed information about the locations of different chemical species
on a surface. The technique uses high-energy (typically up to 30?keV)
beams of positive ions directed at the sample's surface to free secondary
ions from any material that they collide with. These ions are then
accelerated into a time-of-flight analyser and separated according to
their mass-to-charge ratio, producing a spectrum that is indicative of
the sample's chemical composition.

Images generated using ToF-SIMS were shown to display evidence of
friction ridge and sweat pore level detail on samples where fingermarks
were not visible when developed using a conventional technique involving cyanoacrylate and the dye Basic Yellow 40 (BY40).

Experiments were performed over a period of seven months to determine
how fingermarks deposited on the surface of Webley MkII revolver rounds
change over time. The ToF-SIMS technique is also non-destructive and no evidence of image degradation was observed over this period, even when
samples were repeatedly exposed to UHV conditions.

Dr James Sharp has been developing this new technique for several
years and said: "It's really exciting to be taking this research
a step further by adding the rotational stage. We already proved
in our previous research that ToF-SIMS imaging provides much more
accurate and detailed fingerprint images on different types of
surface. This new rotational capability allows us to image in even
more detail and over whole surface areas of difficult materials
and shapes whilst keeping the evidence intact. This could really
pave the way for a new reliable way to analyse evidence, identify
persons of interest and link them to the ammunition in a firearm." ========================================================================== Story Source: Materials provided by University_of_Nottingham. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Charles J. Lee, David J. Scurr, Long Jiang, Andrew Kenton, Shaun
R. T.

Beebe, James S. Sharp. Imaging mass spectrometry of fingermarks
on brass bullet casings using sample rotation. The Analyst, 2021;
DOI: 10.1039/ D1AN01768C ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/11/211115123453.htm

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