UPDATES ON CLPEX.com

No major updates on the website this week.

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Cindy Rennie brought us notes on Daubert issues from the recent ABFDE conference.

we look at a review on MXRF related to latent print examination.

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Excerpts from a term paper on Micro-X-Ray Fluorescence Techniques
by Genise Caruso

Purpose: Research and evaluate a novel [latent print development] method developed by University of California scientists.

The technique, known as micro-x-ray fluorescence, (MXRF) was introduced at the 229th national meeting of the American Chemical Society, in San Diego, on March 13, 2005. Claimed to be revolutionary for detecting fingerprints that are difficult to distinguish through conventional means, the process may conceivably promote further use of fingerprinting as a forensic investigational tool. (Bernstein, 2005)

Science Daily.com website was made in the class discussion area, and through this website I discovered micro-x-ray fluorescence technology was recently developed as a novel method for detecting fingerprints with great advantages over methods that are known.

I had much difficulty finding useful data about MXRF. The information I did come across all appeared to be duplicated from an article written as a direct result of the research presented at the 229th national meeting of the American Chemical Society, in March of 2005.

I sent an email directly to Mr. Christopher Worley, the lead scientist responsible for the research on micro-x-ray fluorescence used in fingerprint identification. If anyone could offer me the information I was seeking, he was the one. Discouraged, as I did not get a response right away, my patience paid off as he did finally reply and provide me with some very valuable information.

Five researchers at Los Alamos National Laboratory in New Mexico, led by analytic chemist, Christopher Worley, Ph.D. developed a new method using X-ray technology that may greatly reduce or eliminate [many existing latent print development] obstacles. Micro-x-ray fluorescence (MXRF) is a procedure that employs spectroscopy, shown in [the below] figure, and while spectroscopic technology, in general, isn’t new, this work was unique, as it appeared to be the only known study concerning the actual detection of fingerprints using MXRF. (Worley et al, 2006)



Bits of residue from things we touch, and human secretions like sweat, blood or saliva, all contain certain chemical components, such as sodium and potassium chloride. MXRF works by detecting fingerprints based on the chemical ingredients connected to the residue, rather than by visible contrast between the print and background, which isn’t always possible. MXRF exposes the chemical markers, displaying ridge patterns of prints, allowing a visible image to be “seen.” (Bernstein, 2005)

Saturating a specimen using a thin beam of X-rays is noninvasive and won’t alter or damage [latent] prints like dusting can. Moreover, since MXRF is based on detecting elements that are left from fingerprints and not the actual prints themselves, it has the ability to uncover evidence on those difficult to detect surfaces.

Worley and his associates succeeded in proving that using MXRF they were able to detect prints unlikely to be discovered under normal assessment methods. Of course this didn’t mean no limitations were found. MXRF has shortcomings. It can’t detect every known element, and some prints just don’t contain enough material to be identified even using this technology. The equipment is very big, must accommodate the sample size, and doesn’t offer capabilities at this time to analyze specimens on location, at the crime scene.

Before it can acquire certification for use in U.S. crime labs, more studies and work is necessary. Additional testing and fine-tuning is needed for commercial use, especially since the current cost is $175,000. If all goes well, Worley and his associates anticipate it could be available for use in fingerprint detection sometime within this decade. He said, “This process represents a valuable new tool for forensic investigators that could allow them to nondestructively detect prints on surfaces that might otherwise be undetected by conventional methods. It won’t replace traditional fingerprinting , but could provide a valuable complement to it.”

A Kevex Omicron instrument (now owned by Thermo Electron) was used to analyze a majority of the samples. An EDAX Eagle II XPL MXRF instrument was used to compare or supplement the Kevex Omicron MXRF images collected from several samples. The Eagle is available in two standard configurations: Eagle II and Eagle II XPL. This table illustrates the basic components for the Eagle II XPL. (EDAX, 2007)

Tube: 40 W X-ray tube (Mo or Rh)
Capillary Optics: X-ray Poly-capillary Lens (XPL) - 40 µm spot
Intensity is roughly 50 to 100 times that of 300 mm mono-capillary
Stage High Precision stage (3 to 5 µm)
Low Mag CCD 10x (B/W)
High Mag CCD 200 x (color)
Chamber: Standard large sample chamber:
Diameter: 330 mm (13.0") Depth: 350 mm (13.8")
Accepts samples up to 250 mm x 200 mm x 90 mm
Detector: 80mm Lithium-drifted Silicon crystal, liquid nitrogen cooled
Na to U simultaneous detection (Be window )
<155 eV resolution for MnKa @ 5000 CPS
<240 eV resolution for MnKa @ 100,000 CPS
Electronics: EDAX Data Acquisition Module (EDAM) III
High throughput digital pulse processor
Multi-DSP and SMT technology
PCI-bus based connection to CPU
Workstation: Windows NT-based workstation fully-integrated with EDAX Data Acquisition Module via PCI interface System configuration and calibration software, comprehensive qualitative and quantitative software, optional Line scan and Mapping


References

Bernstein, M. (2005). New fingerprint visualization method uses Xrays to reveal missing clues. EurekaAlert! Retrieved on January 23, 2007, from http://www.eurekalert.org/pub_releases/2005-03/acs-fv30805.php

CSI: X-Ray Fingerprints. (2006). Micro-x-ray fluorescence also provides spectroscopic information. Science Insider. Retrieved on January 31, 2007, from http://webster.aip.org/dbis/stories/2006/15248.html

EDAX. (2007). Hi-Tech Instruments. (HTI) Micro X-Rays Fluorescence System, Eagle. Retrieved on January 23, 2007, from http://www.htiweb.com/Product_Infor/mXRF/mXRF_Infro.htm

Jones, W.D. (2005). X-ray vision picks up clues to crimes. Spectrum. Retrieved on January 31, 2007, from http://www.spectrum.ieee.org/print/2672

Worley, C.G., Wiltshire, S.S., Miller, T.C., Havirilla, G.J., & Majidi, V. (2006). Detection of visible on latent fingerprints using micro-x-ray fluorescence elemental imaging. Journal of Forensic Sciences. Vol. 51, No. 1, Retrieved on January 31, 2007, from http://www.blackwell-synergy.com