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Summary

Work to advance metrology for forensic fiber trace evidence has been underway since July 2015 through efforts to establish novel comparison metrologies for fibers and evaluation of the uncertainty in commonly used techniques.  One such effort has been our work to look at the phenomenon of photofading in cellulosic fibers when analyzed by microspectrophotometery. 

Description

Forensic evidence is a crucial component of criminal trials. The STG performs research to advance the metrology for forensic fiber trace evidence, reduce uncertainty in applicable measurement systems, and guide forensic examiners.  The STG works with the forensic trace evidence, academic, and industrial communities to help advance the metrology for forensic fiber trace evidence through participation in standardization bodies and has co-organized several workshops in the area of trace evidence. . The STG has several projects in this focus area, which include the evaluation of uncertainty in commonly used techniques, the assessment of advanced metrologies for forensic fiber examination, and the development of guidelines for understanding the effects of environmental exposure on fiber comparisons.

Major Accomplishments

We have performed a series of studies to investigate the phenomenon of photofading on dyed fibers in the microspectrophotometer.

  • Examined photobleaching in three direct dye systems on cellulose:  Three colors: Direct Blue 71, Direct Red 81, and Direct Yellow 27

    Direct Blue 71, Direct Red 81 and Direct Yellow 27
    Fabrics dyed for the photofading study

  • Photofading work has been summarized in several presentations:
  • Poster at Fall 2016 Forensics at NIST conference (11/2016)
  • Presentation at 2017 AAFS meeting (02/2017)
  • Presentation at 2017 American Association of Textile Chemists and Colorists (AATCC) meeting (03/2017)
  • This work was recently published in the journal Forensic Chemistry
  • All of the data associated with this publication is available at this link, and is associated with this DOI, 10.18434/M3W88G.

Forensics chemical structures
Chemical structures of dyes used in the photofading study

Forensics red fiber
Red fiber showing photofading after 30 minutes of exposure to the MSP light source.

 

Created March 23, 2017, Updated August 14, 2017