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Use of Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS) Methods for the Analysis of Small Particles Adhering to Carpet Fiber Surfaces as a Means to Test Associations of Trace Evidence in a Way That is Independent of Manufactured Characteristics

NCJ Number
Date Published
June 2012
77 pages
This project developed and tested an innovative instrumental trace-evidence approach for the recovery and quantitative analysis of very small particles (VSP) that adhere to carpet fibers.
VSP, which can be smaller than conventional trace evidence, are virtually ignored by forensic science. The project developed methods for quantitatively removing VSP from carpet fibers and prepare them for analysis by SEM/EDS (scanning electron microscopy/energy dispersive spectroscopy); and it used existing computer-assisted SEM/EDS method for testing whether the resulting VSP profiles are useful in quantitatively associating shed fibers with a source carpet. The study demonstrated the regular occurrence of hundreds to thousands of VSP on individual carpet fibers. The quantity and character of VSP was sufficient to associate fibers with their carpet area of origin. The findings led to a rejection of the hypothesis that there is a strictly quantitative relationship among VSP, as measured using environmental particle profiles. Environmental particle profiles were found to be unsuitable for assessing VSP variability. An alternative method was developed based on target particle types (TPTs) defined by their elemental profiles, which were measured by computer-assisted SEM/EDS. Within-carpet and between-carpet variations showed an approximately even distribution for most TPTs, and between-carpet variations showed a wide range in types and quantities of VSP. The usefulness VSP in linking carpet fiber evidence has been established. There is now an achievable potential to use VSP for independent, quantitative testing of the common origin of carpet fibers. There is a set of follow-up research steps that have been outlined and ready to be undertaken. 34 tables and 32 references

Date Published: June 1, 2012