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Metrology

Analytical Forensic Metrology 4 th International Conference on Forensic Research & Technology September 29, 2015 Jerry D. Messman, PhD Stranaska Scientific LLC Fort Collins, Colorado USA. BIPM. RMO Labs. NMI Labs. Commercial Metrology Labs. In-House Central Metrology Lab.

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Metrology

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  1. Analytical Forensic Metrology4th International Conference onForensic Research & TechnologySeptember 29, 2015Jerry D. Messman, PhDStranaska Scientific LLCFort Collins, Colorado USA Stranaska Scientific LLC

  2. BIPM RMO Labs NMI Labs Commercial Metrology Labs In-House Central Metrology Lab Forensic Testing Labs Metrology science of measurement and its application Etymology Greek “metron” (measure) Includes all theoretical and practical aspects of measurement • All fields of application including routine measurement • All sectors of measurement whatever the relative magnitude of the measurement uncertainty. Stranaska Scientific LLC

  3. Measurement Accuracy Stranaska Scientific LLC

  4. Quality in Forensic Laboratories • Implementing Laboratory Accreditation • ASCLD/Lab-International • International Standard ISO/IEC 17025:2005 General requirements for the competence of testing and calibration laboratories • Embracing Metrological Concepts • Measurement Traceability • Measurement Uncertainty Stranaska Scientific LLC

  5. Metrological Traceability Definition property of a measurement result whereby the result can be related to a reference through a documented unbroken chain of calibrations, each contributing to the measurement uncertainty Stranaska Scientific LLC

  6. Metrological Traceability Essential Elements • Unbroken Chain of Comparisons • Documented Measurement Uncertainty • Documented Measurement Procedure • Technical Competence • Realization of SI Units • Documented Calibration Intervals • Measurement Assurance Stranaska Scientific LLC

  7. Establishing TraceabilityCALIBRATION Stranaska Scientific LLC

  8. Metrological Traceability Stranaska Scientific LLC

  9. Calibration Standards SRM 1828b Ethanol-Water Solutions (Blood-Alcohol Testing: Six Levels) Ethanol-50 Certified Reference Standard NIST Traceable Stranaska Scientific LLC

  10. Spectrophotometric Analysis COMMERCIAL INSTRUMENTS • Reader • Analyzer • Spectrophotometer Stranaska Scientific LLC

  11. Spectrophotometer Qualification UV Absorption Spectrum of Cocaine in 0.1 M HCl UV Transmittance Spectrum of Holmium Oxide Solution Stranaska Scientific LLC

  12. Measurement Uncertainty non-negative parameter of characterizing the dispersion of the quantity values being attributed to a measurand, based on the information given Stranaska Scientific LLC

  13. Measurement Uncertainty Requirement • ISO/IEC 17025:2005 Recommendation • Voluntary quality system • Analytical metrology framework Prerequisite to Evaluation of MU • Metrological traceability Professor Paul De Bievre CITAC Workshop, 21 January 2010 Weizmann Science Park, Ness Ziona, Israel Stranaska Scientific LLC

  14. Measurement Uncertainty Stranaska Scientific LLC

  15. Measurement Uncertainty General Approaches to Estimation of MU • TOP-DOWN • Replication of the whole measurement process Empirical / Experimental / Retrospective • BOTTOM-UP • Quantification of individual uncertainty components Modeling / Theoretical / Predictive Stranaska Scientific LLC

  16. Evaluation of Uncertainties Type A An uncertainty evaluated by statistical analysis of a series of observations • Normally used to obtain a value for the repeatability or randomness of a measurement process Type B An uncertainty evaluated by non-statistical means (methods other than statistical analysis of a series of observations) • Evaluation of standard uncertainty is based on some other scientific knowledge Stranaska Scientific LLC

  17. Uncertainty Budget • Tabular summary of different individual sources of uncertainty and their estimated magnitudes for a given measurement or calibration process • Coverage factor – level of confidence (e.g., 95%) • Expanded uncertainty – best estimate for interval containing calibration reference value Stranaska Scientific LLC

  18. Reporting of Results • Report the value of the measurand and expanded uncertainty Y ± U • Report the statement of confidence Example: The reported expanded uncertainty is based on a standard uncertainty multiplied by a coverage factor k=2, providing a coverage probability of approximately 95% Stranaska Scientific LLC

  19. Reporting of Results RegardingSpecification or Statute Limit Stranaska Scientific LLC

  20. Measurement Uncertaintyin the Courtroom State of Washington v. Weimer #7036A-09D Memorandum Decision on Motion to Suppress March 23, 2010 Blood alcohol content (BAC) measurement (GC) Result of blood test is not admissible in the absence of a scientifically determined confidence level. Defense Attorney Ted Vosk Stranaska Scientific LLC

  21. Measurement Uncertaintyin the Courtroom State of Washington v. Fausto et al Case No. C076949 and 9Y6231062 Order Suppressing Defendant’s Breath-Alcohol Measurements in the Absence of a Measurement for Uncertainty September 21, 2010 . . . the State must provide Defendants with a confidence interval for each Defendant’s breath-alcohol measurement. Absent this information, a defendant’s breath-alcohol measurement will be suppressed. Stranaska Scientific LLC

  22. Measurement Uncertaintyin the Courtroom State of Michigan v. Jabrocki File No. 08-5461-FD Opinion May 6, 2011 Defense Attorney Mike Nichols This court therefore finds that the blood test results are not reliable until the state police crime lab calculates an uncertainty budget or error rate and reports that calculation along with the blood test results. This court specifically finds that calculation of an uncertainty budget or error rate and the reporting of the same is an essential element of the scientific methodology for analyzing blood alcohol content using gas chromatography. Stranaska Scientific LLC

  23. Concluding Remarks Measurement Data Integrity Metrologyis an infrastructural science, and an enabling science, which underscores the scientific integrity, validity and defensibility of analytical measurement results. Key Points for Metrological Consideration • Scientific Rigor • Timeline • Transparency • Healthy Scientific Skepticism Thank You! Stranaska Scientific LLC

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