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Exploitation of Very Small Particles To Enhance the Probative Value of Carpet Fibers

NCJ Number
Date Published
June 2015
66 pages
This is the final report on a NIJ-funded project that refined the process for examining very small particles (VSPs) on carpet fibers to aid in comparing them with a source carpet, and it applied this process under realistic casework conditions, resulting in the creation of a work prototype for both the analytical methods and the measurement of the probative value of comparisons.
The overall conclusion of the project is that it has established the usefulness of VSPs in providing objective, quantitative associations and measurements of probative value, thus removing fundamental limitations to the probative value of carpet-fiber evidence. Field collections of carpet fibers were conducted by crime-scene practitioners under realistic casework conditions. VSPs were isolated and analyzed using SEM/EDS analytical protocols in an operational crime laboratory. Computational methods were designed to allow sets of hundreds to thousands of VSPs to be characterized. Classifiers were designed to associate and discriminate among specimens. Quantitative measures of correspondence and probative value were designed and successfully applied to VSP data. Particle sets larger than 500 showed strong promise for quantitative associations with their sources. The use of larger numbers of target particle types showed promise for improving the performance of classification and association. 23 figures, 11 tables, and 22 references

Date Published: June 1, 2015