Forensics Detection and Sensor Systems: Industrial Sensor Development at Lawrence Berkeley National Laboratory

Description:
Different detection systems have been devised to study forensics-related chemistries, materials, and national and homeland security issues. The methods are non-invasive and do not destroy or alter the sample being studied.

Broad Fields of Use:
Sensors and sensor-related techniques can be devised to look at materials and chemicals that are pertinent to the field of forensics science, and studies conducted in conjunction with crime scenes. Many types of substances may be detected and analyzed, including blood, fingerprints, other bodily fluids, and non-biological substances such as inks, paper, and others that may be associated with a crime scene. Additionally, these same techniques can be readily applied to issues of national and homeland security and tagging to identify ownership by an individual or corporation.

Figure 1. Infrared spectromisrocopy has proven effective at characterizing evidence from crime scenes such as blood, fabrics and soil particles. Infrared light from a thermal source or a synchrotron beam enters the Michelson interferometer from the right. The modulated light leaves the interferometer and enters an infrared microscope, where it is focused onto a sample. The sample absorbs certain frequencies of light and the outgoing components of light are focused onto an infrared detector. Visible images of the sample can also be taken at the same time. The sample is positioned on a computer-controlled microstage so that the infrared spectrum can be mapped with micron precision.

Comparison with Current Technologies:
Techniques that we have developed at Berkeley Lab for the detection and examination of forensics-related chemicals, traditional materials, and biomaterials exceed detection limits of currently available commercial products. The techniques can be used to study any solid or liquid evidence, including milligram-scale or considerably smaller amounts of evidence. Our techniques can be used to analyze down to a micron lateral resolution or tens of microns at the very "worst" case low resolution. In cases such as inks, the sampling and detection can be conducted non-destructively, with direct analysis of the ink on paper with no harm to the paper.

Description of Current Application:
We have developed techniques that can be used with either a fixed instrument for real-time detection and analysis of forensics-related substances or for the use of field-deployable instruments that can detect and analyze inks, blood, and other chemical component evidence. Microsampling techniques and materials also have been developed.

Figure 2. The absorbance of an ink-soaked paper fibre (inset) as a function of wavenumber, the number of waves per centimetre. The green spectrum was obtained using infrared microscopy at the Advanced Light Source, a synchrotron source that is some 200 times brighter than a conventional black body. In contrast, the red spectrum was measured under the same experimental conditions and over the same period of time but with a conventional thermal source. The improvement in brightness at the synchrotron enhances the signal-to-noise ratio for small samples.

The techniques developed for forensics applications perform rapid, in situ measurements of a variety of materials and fluids with no preliminary chemistry or separation needed. Current applications show good sensitivity and discrimination of different members of forensics sets of various inks, papers, fingerprints, and other systems of interest. The use of different sampling materials also will allow–if desired–separations and subsequent sensor detection of the components of a sample.

MS 70A1150
Sensors Group
Lawrence Berkeley National Laboratory
Berkeley, CA 94720