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New Techniques

Development and implementation of new techniques for analysis of physical evidence and for defense.
(Armstrong, Baldwin, Chumbley, Coats, Houk, McClelland, Nilsen-Hamilton, Thiel, R.B. Thompson, Yeung)

In many cases, the composition of a material can be used to establish its provenance. For instance, one might use this approach to identify the synthetic chemistry of an illegal drug, or to ascertain illicit production of nuclear weapons from dust residue. In this arena, ISU is very strong. Part of our strength derives from the 50-year history of the Ames Laboratory, a DOE Laboratory on campus that emphasizes materials science. Another source is the Department of Chemistry's historical strength in analytical chemistry, which is reflected in its current ranking as 5^th in the nation for this specialty.

Serial Numbers
One specific area of research at ISU has been the recovery of information about serial numbers that have been mechanically removed from metal parts. For example, a serial number stamped or scribed on a surface might be filed off. However, even if the visible surface imprint has been removed, a microstructural record of the serial number often remains. The surface deformations that occur when the serial number is created are accompanied by additional subsurface deformations through such processes as dislocation formation and grain rotation. Moreover, we have demonstrated experimentally that these changes can be sensed nondestructively by the propagation on the material under examination. Future work calls for a quantitative understanding of the mechanism in relation to materials properties.

Trace Elements
Trace element analysis has great potential for use in forensic analysis. Inductively-coupled-plasma Mass Spectrometry (ICP-MS), used in conjunction with laser ablation for sample introduction, is seeing extensive use for matching evidence based on trace element composition. It has the key advantages of high sensitivity and the ability to analyze solids without destroying the evidence. At ISU, we have developed multivariate methods based on principal components analysis to do so using the entire suite of observable elements, not just a chosen few. We have also demonstrated a general procedure for quantitative calibration of elemental concentration using dried aerosol particles from nebulized solutions. Measurement of actual quantitative concentrations, in addition to peak patterns, lends credence to evidence during testimony. Isotopic composition can also be measured by ICP-MS. It may be possible to trace or match bullets based on a combination of trace element concentrations and lead isotopic composition, as the abundances of the four stable lead isotopes vary widely in nature. Work has already been done on materials provided by the FBI and the Illinois Crime Lab.

Trace analysis is also being employed at ISU for inks. Specifically, the ink work involves developing (i) new instrumentation for FT-IR spectroscopy of various types of ink applied to different paper stock, (ii) reproducible methods to measure spectra for building data bases and for analysis of unknowns, and (iii) search routines that are as robust as possible in the presence of factors that are hard to control such as the condition of specimens presented for analysis.

Defense
Analysis techniques are important for defense as well as forensics, when chemical and biological weapons are considered. If such weapons are used, an attack can be difficult to detect, and the antidote or prophylactic may depend upon the precise nature of the weapon. One of the major issues in detecting microbes in bioterrorism, for instance, is the need to quickly identify the specific agent involved. Present DNA sequencing and genetic typing protcols are still costly, time consuming, and labor intensive. We are developing novel microcapillary systems and nucleic acid sensors for direct genotyping of low numbers of microbes. These systems will be fully integrated so that they can be mounted in vans to be operated on the scene of the crime. Genetic analysis can be completed in two hours with 96 samples being analyzed at a time. This will greatly facilitate detecting and tracing any biogenic material, from bacteria to blood.