Bulletproof fingerprint technology takes images in circles

Experts have developed a unique method for recovering high-resolution fingerprint images from curved objects like bullet casings that offers greater detail and accuracy than traditional forensic methods.

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

Recovering fingerprint evidence from bullet casings is a major area of ​​difficulty for forensic scientists. While fired and unfired casings can often be found at violent crime scenes, retrieving fingerprints and linking the person who loaded the weapon to the crime has always proven difficult due to the physical conditions encountered. through the casings during firing. and techniques used to develop and image fingerprints.

When a bullet is fired, the casing experiences high temperatures, pressures and significant frictional forces inside the barrel of the weapon. They can also be coated with propellant residue and gunpowder which is 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 fingerprint residue (such as water, amino acids, and low molecular weight organic compounds such as lipids), as well as potential smudging or obscuring of the mark. These factors can complicate the operation of conventional fingerprint retrieval methods such as cyanoacrylate (superglue) smoke and fluorescent staining approaches.

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) positive ion beams directed at the sample surface to release secondary ions from any material they collide with. These ions are then accelerated in a time-of-flight analyzer and separated according to their mass-to-charge ratio, producing a spectrum indicative of the chemical composition of the sample.

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

Experiments were carried out over a period of seven months to determine how fingerprints deposited on the surface of Webley MkII revolver cartridges change over time. The ToF-SIMS technique is also non-destructive, and no evidence of image degradation was observed over this period, even when the 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 take this research one step further by adding the rotation step. We have already proven in our previous research that ToF imaging -SIMS provides much more accurate information and detailed fingerprint images on different types of surfaces.This new rotational capability allows us to image in even greater detail and on entire surfaces of difficult materials and shapes while keeping intact evidence. This could really pave the way for a reliable new way to analyze evidence, identify persons of interest, and link them to firearm ammunition.”

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Material provided by University of Nottingham. Note: Content may be edited for style and length.

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