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2007/2008 SWGDRUG
ACCOMPLISHMENTS
sponsored by the
Drug Enforcement Administration
Office of Forensic Sciences
and the
National Institute of Standards
and Technology
SWGDRUG
Scientific Working Group for the
Analysis of Seized Drugs
WHY UNCERTAINTY
NEXT?
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Forensic community asking for guidance
Accrediting bodies establishing measures of
assessing conformity with ISO
Customer requirements
Jurisdictional requirements
Transparency (nothing to hide)
 Potential Exculpatory Information
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Uncertainty Document
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The core committee voted in January 2008 to release
the draft uncertainty document for public comment
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Posted on the website since February 2008
The SWGDRUG meeting was held July 21-23, 2008 in
New Orleans, LA
Comments were addressed and the core committee
voted to adopt the document on July 22, 2008
The document should be posted on the website by the
end of August 2008
SWGDRUG APPROACH
TO UNCERTAINTY
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There is a wealth of information that already exists
on Uncertainty
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No intentions of repeating existing information
Goal is to tailor the recommendations to drug
analysis and answer specific uncertainty questions
Answer specific drug analysis uncertainty questions,
before others do
Offer guidance and direction to laboratories and
accrediting bodies
WHY?
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Provide Purpose/Guidance
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Raise Awareness
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Uncertainty is not doubt, it provides assurance that
results and conclusions are fit for purpose
Laboratory Responsibility
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Uncertainty is associated with both qualitative and
quantitative procedures
Consider customer requirements and address uncertainty
through training, procedures and documentation
Benefits
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Enhanced confidence through increased understanding
of results
Provides Mechanism to express reliability of results
HOW?
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Two Primary Sections
Qualitative
 Quantitative
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Purity
 Weights
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QUALITATIVE
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Individual methods have limitations and,
consequently, uncertainty
Understanding limitations allows analysts to
build an appropriate analytical scheme to
correctly ID drugs or chemicals
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It is expected that an appropriate analytical
scheme will result in, effectively, no uncertainty
in reported identifications
Relevant limitations of an analytical scheme
should be documented and may need to be in
report
QUALITATIVE
EXAMPLES
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Use Part III B Methods of Analysis/Drug
Identification
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IR and microcrystalline test positive for cocaine
– effectively NO uncertainty
Limitations
Marquis test positive for methamphetamine –
could be methamphetamine or other
amphetamines
 GC/MS test positive for ephedrine – could be
ephedrine or pseudoephedrine
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QUANTITATIVE
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Uncertainty is defined as an estimate
attached to a test result which characterizes
the range of values within which the true
value is asserted to lie
Precise calculations of
measurement uncertainty
is not always required
QUANTITATIVE CONT.
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Primary numerical values reported in the
analysis of seized drugs are
 Weight
and
Purity
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Where a value is critical, an appropriate
measurement uncertainty determination shall
be applied
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Weight close to a statutory threshold
Purity of drug affects sentencing
WEIGHT
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Uncertainty of a reported value is dependant on the
weighing process. Factors include:
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Single item versus multiple items (# of weighing
operations)
Tare function as separate weighing operation
Extrapolation of population weight from limited sampling
of multiple items
Aggregate weighings
Incomplete recovery of material from packaging
Balance selection (e.g., readability, capacity)
Balance operation (e.g., sample placement, environmental
conditions)
PURITY
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Sources of uncertainty for purity determination
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Sampling plan (e.g., handling of multiple exhibits)
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Sample homogeneity
Analytical method
Sample preparation (e.g., size, matrix effects, solubility)
 Analytical technique
 Reference material (e.g., purity of standard)
 Equipment and instrumentation performance (e.g.,
glassware, pipetters, balances, chromatographs)
 Concentration of analyte
 Environmental conditions
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PURITY APPROACHES
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Analytical Error
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Sampling Error
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Address both systematic and random error
through method validation and quality assurance
The sample and sampling procedure are often the
greatest contributors to measurement uncertainty
Where appropriate, confidence levels (e.g.,
95%) shall be selected based on
considerations relevant to the analytical
context
Record uncertainty information in
validation documents and/or case records
UNCERTAINTY BUDGET
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All sources of error are separately identified
and tabulated
Assign values to each error source using
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Empirical data
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Validation process, Historical performance data, Control
chart data, proficiency tests
Published data
 Combination of empirical and published data
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Can exclude insignificant sources
Calculate combined and expanded uncertainty
using significant values for procedure
NON-BUDGET APPROACH
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Example 1: Use of data from replicate analyses
from a validated method with an appropriate
sampling plan
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Sources of uncertainty that are separately assessed
in the budget method are collectively assessed by
experimental measurements
Example 2: Use of two standard deviations (2σ)
of the test method results from reproducibility
data from the validation studies.
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Provides an approximation of the measurement
uncertainty for non-critical values
WHEN?
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Reporting of measurement
uncertainty
 Uncertainty shall be documented
but may not need to be reported
 Should be reported when result
impacts customer
 If not reported, analysts shall be
cognizant of the uncertainty
associated with their results
REPORTING
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Factors to consider when reporting:
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Jurisdictional
Prevailing statutory requirement
 Relevant governing body (agency) requirements
 Customer requests
 Potential exculpatory value
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Analytical
Qualitative results where limitations are known (e.g.,
inability to differentiate isomers)
 Quantitative measurements where a value is critical (e.g.,
weight or purity level close to statutory threshold)
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Laboratory accreditation requirements
REPORTING EXAMPLES
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Qualitative:
Contains Ephedrine or Pseudoephedrine. Item
tested: 5.2 grams net
 Visual examination determined that the physical
characteristics are consistent with a Schedule IV
pharmaceutical preparation containing Diazepam.
There was no apparent tampering of the dosage
unit and no further tests are being conducted.
 Contains cocaine (salt form not determined)
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REPORTING EXAMPLES
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Quantitative:
Positive for cocaine in the sample tested
Net weight of total sample: 5.23 grams ± 0.03 grams
Quantitation: 54.7% ± 2.8%
 Sample tested positive for cocaine
Net weight: 5.23 grams
Purity: 54.7%
Confidence Range: ± 2.8%*
Calculated net weight of drug: 2.8 grams of cocaine
*Confidence range refers to a 95% confidence level
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TRAINING
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Individuals responsible for determining, evaluating
and documenting uncertainty shall be capable of
demonstrating familiarity with foundational
concepts and principles of estimating uncertainty
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General metrology (terminology, symbols, etc.)
Concepts of random and systematic error, accuracy,
precision, propagation of error, etc.
Reporting conventions (sig. figs, truncating, rounding)
Basis statistics (i.e., confidence interval, probability, etc)
Analysts shall be capable of explaining their labs
procedures for evaluating uncertainty of
qualitative and quantitative analyses
SUPPLEMENTAL
DOCUMENTS TO FOLLOW
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Control chart data method
Demonstration of balance control using
standard weight sets
Summing weights from individual exhibits
Expression of sampling uncertainty based on
confidence interval using multiple samplings
Uncertainty budget
CORE COMMITTEE
• DEA – Nelson Santos (Chair)
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Secretariat – Scott Oulton (non-voting)
FBI - Eileen Waninger
ASCLD – Garth Glassburg
NIST - Susan Ballou
ASTM and NEAFS- Jack Mario
Educator – Dr. Chris Tindall
Educator – Dr. Suzanne Bell
CORE COMMITTEE
• CAC & NWAFS - Jerry Massetti
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MAFS - Richard Paulas
MAAFS - Linda Jackson
SAFS – Christian Matchett
Toxicology – Dr. Robert Powers
CORE COMMITTEE
• Canada - Richard Laing
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Japan – Mr. Osamu Ohtsuru
United Kingdom - Dr. Sylvia Burns
Australia - Catherine Quinn
Germany - Dr. Udo Zerell
ENFSI - Dr. Michael Bovens
UNODC - Dr. Iphigenia Naidis
THANK YOU
Visit Us At
www.swgdrug.org