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In forensic science, knowledge and understanding of material transfer and persistence is inherent to the interpretation of trace evidence and can provide vital information on the activity level surrounding a crime. Detecting metal ions in fingermark residue has long been of interest in the field of forensic science, due to the possibility of linking trace metal ion profiles to prior activity with specific metal objects (e.g. gun or explosive handling). Unfortunately, the imaging capability to visualise trace metal ions at sufficient spatial resolution to determine their distribution within a fingermark (micron level) was not previously available. Here, we demonstrate for the first time transfer and persistence of metals in fingermarks, at micron spatial resolution, using synchrotron sourced X-ray fluorescence microscopy. Such information may form a critical baseline for future metal-based detection strategies. Fingermarks were taken before and after brief handling of a gun barrel, ammunition cartridge case and party sparkler to demonstrate the transfer of metals. The results reveal increased metal content after contact with these objects, and critically, a differential pattern of metal ion increase was observed after handling different objects. Persistence studies indicate that these metals are removed as easily as they are transferred, with a brief period of hand washing appearing to successfully remove metallic residue from subsequent fingermarks. Preliminary work using X-ray absorption near edge structure spectroscopic mapping highlighted the potential use of this technique to differentiate between different chemical forms of metals and metal ions in latent fingermarks. It is anticipated that these findings can now be used to assist future work for the advancement of trace metal detection tests and fingermark development procedures. This journal is

Copyright © 2019 American Chemical Society. Fingermarks are an important form of crime-scene trace evidence; however, their usefulness may be hampered by a variation in response or a lack of robustness in detection methods. Understanding the chemical composition and distribution within fingermarks may help explain variation in latent fingermark detection with existing methods and identify new strategies to increase detection capabilities. The majority of research in the literature describes investigation of organic components of fingermark residue, leaving the elemental distribution less well understood. The relative scarcity of information regarding the elemental distribution within fingermarks is in part due to previous unavailability of direct, micron resolution elemental mapping techniques. This capability is now provided at third generation synchrotron light sources, where X-ray fluorescence microscopy (XFM) provides micron or submicron spatial resolution and direct detection with sub-μM detection limits. XFM has been applied in this study to reveal the distribution of inorganic components within fingermark residue, including endogenous trace metals (Fe, Cu, Zn), diffusible ions (Cl-, K+, Ca2+), and exogeneous metals (Ni, Ti, Bi). This study incorporated a multimodal approach using XFM and infrared microspectroscopy analyses to demonstrate colocalization of endogenous metals within the hydrophilic organic components of fingermark residue. Additional experiments were then undertaken to investigate how sources of exogenous metals (e.g., coins and cosmetics) may be transferred to, and distributed within, latent fingermarks. Lastly, this study reports a preliminary assessment of how environmental factors such as exposure to aqueous environments may affect elemental distribution within fingermarks. Taken together, the results of this study advance our current understanding of fingermark composition and its spatial distribution of chemical components and may help exp

High-resolution trace element mapping (2 micron beam) was performed by synchrotron radiation X-ray fluorescence microscopy (SXFM) on Cu- and Zn-rich chimneys from Brothers volcano. The maps cover 84- to 136-mm2 cross sections of the inner chimney walls and document the distribution of Fe, Cu, Zn, As, Se, Sr, Pb ± Ga, Au, Bi, and U. Comparative element maps were generated by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) at a lower resolution (47 micron beam), which additionally measured Co, Ni, Mo, Ag, Cd, In, Sn, Sb, Ba, Au, Tl ± V, Te, and Bi. In two Zn-rich chimneys, Cu distribution varies from Cu-bearing sphalerite with chalcopyrite disease to distinct chalcopyrite-lined channels, implying a progression of chalcopyrite replacement of sphalerite. Conversely, the two Cu-rich chimneys have different styles of massive chalcopyrite lining their conduits. Fine (15-40 micron) trace element rings are revealed within and between laminations that exhibit variable contents and distributions of Co, Ni, Zn, As, Se, Mo, Ag, Cd, Sn, Te, Au, Tl, Pb, Bi, and U. The trace element rings are a proxy for the secular evolution of vent fluid compositions. Enrichment factors of trace element rings were compared to those of fumarole condensates studied at subaerial arc and rift volcanoes and molten S pooled atop a submarine back-arc volcano. Our enrichment factors show remarkable consistency with the other volcanoes and indicate Au, Te, Bi, Cu, Ag, and Se in Brothers’ chimneys were magmatically derived., High-resolution trace element mapping (2 micron beam) was performed by synchrotron radiation X-ray fluorescence microscopy (SXFM) on Cu- and Zn-rich chimneys from Brothers volcano. The maps cover 84- to 136-mm2 cross sections of the inner chimney walls and document the distribution of Fe, Cu, Zn, As, Se, Sr, Pb ± Ga, Au, Bi, and U. Comparative element maps were generated by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) at a lower resolution (47 micron beam), which additionally measured Co, Ni, Mo, Ag, Cd, In, Sn, Sb, Ba, Au, Tl ± V, Te, and Bi. In two Zn-rich chimneys, Cu distribution varies from Cu-bearing sphalerite with chalcopyrite disease to distinct chalcopyrite-lined channels, implying a progression of chalcopyrite replacement of sphalerite. Conversely, the two Cu-rich chimneys have different styles of massive chalcopyrite lining their conduits. Fine (15-40 micron) trace element rings are revealed within and between laminations that exhibit variable contents and distributions of Co, Ni, Zn, As, Se, Mo, Ag, Cd, Sn, Te, Au, Tl, Pb, Bi, and U. The trace element rings are a proxy for the secular evolution of vent fluid compositions. Enrichment factors of trace element rings were compared to those of fumarole condensates studied at subaerial arc and rift volcanoes and molten S pooled atop a submarine back-arc volcano. Our enrichment factors show remarkable consistency with the other volcanoes and indicate Au, Te, Bi, Cu, Ag, and Se in Brothers’ chimneys were magmatically derived.