Importance of Quality
Assurance for Forensic
Toxicology in North America
Graham R. Jones, Ph.D.
Chief Toxicologist
Office of the Chief Medical Examiner
Edmonton, Alberta, Canada
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This presentation is based on an invited
lecture prepared for and given at the
annual meeting of the Japanese
Association of Forensic Toxicologists in
Fukuoka, Japan, August 27, 2005.
(Reproduced here with only minor changes)
Graham Jones
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Importance of Forensic Toxicology
 Forensic testing is performed for a legal
purpose and may affect:
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Criminal trial (freedom/jail or death of accused)
Civil trial (denial of compensation/money)
Loss of a job (if drug use proven)
Loss of career (e.g. sports/athlete)
Custody of children (if drug abuse proven)
 Toxicology testing must be ACCURATE!
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Types of Forensic Toxicology
Laboratories in North America
 Federal (FBI – U.S.; RCMP – Canada)
 State (U.S.) / Province (Canada)
– Police / Crime lab; Medical Examiner/Coroner
 County / City / Local (U.S.)
– Police / Crime lab; Medical Examiner/Coroner
 Private (mostly in U.S.)
– some have national coverage, some mainly
local
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North American Courts - Adversarial
 In the U.S. and Canada, the court system is
“adversarial”
– Prosecution and defense lawyers may each hire their
own toxicologists who may give different opinions
– Prosecution toxicologists may perform testing and give
an interpretation (opinion)
– Usually defense toxicologists offer only an opinion and
do not usually perform analytical work on cases
 The adversarial system should not affect the
science, but allows more than one scientific
opinion to be expressed in court
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Why does an adversarial court
system make a difference?
 Prosecution laboratory results are more likely to
be challenged by defense
– Prosecution toxicologist may be required to provide all
details of their analysis (chromatograms, methods,
chain of custody etc)
– Many (good) forensic toxicologists are available to
review analytical data for the defense and provide a
second opinion
– Prosecution toxicologists are more likely to have to
defend their analytical work in court
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Everyone makes mistakes!!
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Quality Assurance Program
 Every toxicologist in a laboratory will make a
mistake. The problem is making sure that the
mistake is detected before a result is reported
 A good QUALITY ASSURANCE program will
help to minimize errors and detect errors when
they occur
 “Quality assurance” covers every aspect of
laboratory work that can affect the quality
of the results reported
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Example of a Preventable Error
 A person died in a psychiatric hospital
 Her medications were dispensed by hospital staff
 The pathologist determined death due to natural causes, but
toxicology testing indicated an imipramine overdose!
 A public inquiry was held and data of the toxicologist was
reviewed – finding calculation error of 10-fold
 Public disclosure of the error was very embarrassing for
the toxicologist
 The error could have been discovered before public
embarrassment if the data had been properly peer reviewed
(i.e. by a colleague in the same laboratory).
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Quality Assurance Includes:
 Education and training
 Standard Operating Procedures (SOPs)
 Validation of methods; Criteria for evaluation of
calibrations, controls and case data
 Maintenance of equipment
 Review and reporting of results
– Verifying results of a colleague
– Someone else should check your transcriptions and calculations
 Proficiency testing
 Laboratory accreditation
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Education and Training
 Education in chemistry (and pharmacology)
 Training in the laboratory
– Develop good analytical skills
– Learn acceptance criteria the laboratory uses for
deciding which results are OK and which have to be
repeated! (e.g. what is an acceptable calibration?)
– Learn about the quality assurance program of the
laboratory
 Continuing education
– Additional training, reading, courses, conferences
– May be minimum requirements for personal
certification
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Standard Operating Procedures
 Important that routine analytical methods
and procedures are written and should be
approved by the laboratory director
– Helps to ensure that all toxicologists perform
the assay the same way each time
– Enables the courts to know exactly which
method was used to generate a result in a
particular case
– Makes independent review of the analytical
method easier
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Calibrations – What criteria?
 Need to have consistent criteria for when a calibration
is “acceptable” and whether controls have “passed”
 Several different criteria can be used to ensure that a
calibration is acceptable
– Correlation coefficient – (e.g. >0.98)
– Multipoint calibration (e.g. 3 – 8 points)
– Each calibrator can be read against calibration line (e.g. 80 – 120%
of target)
– Can use linear, exponential or other curve fit
• Not all assays are inherently linear
 But you must use criteria of some kind…
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Quality Control
 Used to verify the precision and accuracy of the
calibration
– Preferably prepared as a “pool” that is verified prior to
first use
– Pre-prepared and frozen for use in many assays
 Analyte spiked into a similar matrix (e.g. blood)
 Should be independently prepared
– Can be a external supplier (purchased material)
– Can be another person in the same laboratory, but the
control should ideally be made from another source
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Controls – What criteria?
 Controls should be prepared by a person other
than the toxicologist conducting the assay
 The source of the standard solution should ideally
be different than that used for the calibration (e.g.
different manufacturer; different lot number)
 Controls should usually read within +/-20% of
target
– Exceptions – alcohol ±5-10%
– Some difficult drugs or controls at very low
concentrations may be ±25%
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Proficiency Test (PT) Programs
 All toxicology laboratories should subscribe to
one or more PT programs appropriate for their
work (e.g. for alcohol and drugs)
 Corrective actions must be performed when results
of the lab significantly different from that
expected (e.g. for drugs >±20% or ±2 SD)
 It is NOT acceptable to review controls and ignore
the results if they are outside the acceptable target
 Some laboratories participate in 3–5 PT programs
 PT programs can be internal, but external better
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Example of Acceptable Proficiency Test Results
Mean value 413 mg/100ml- 2 S.D. range ±10.5% (Acceptable)
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Example of Poor Proficiency Test Results
Mean value 1021 mg/l - 2 S.D. range ±42.6% (POOR)
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Corrective Action
 Bad control or PT results MUST be remediated
– i.e. investigate why the results were out-of-range
 Corrective action could be:
– Review of calibration and data calculation
– Review of chromatograms and integration
– Re-analysis of the sample
– Troubleshooting the assay (precision, accuracy)
– Inter-laboratory comparison of results
 Main reason for bad results: poor precision
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Forensically unacceptable practice
 Once the calibration, controls and case
samples are run:
– Calibrators should not be dropped from the
middle of the curve in order to improve the
correlation coefficient
– Failed controls should not be ignored
– Failed controls should not be re-setup in
isolation of the case sample(s)
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Method Validation
 Analytical methods must be appropriately
validated
– Linearity (upper and lower)
• Is the calibration accurate over the entire reporting range? The
calibration parameters may change at the upper end
(saturation) and lower end (adsorption)
– Accuracy
– Precision
– Specificity
• Is only the target compound being measured?
• Mass spectrometry is increasingly preferred, but must be
properly run
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Linearity
 Especially important to determine if range of
calibrators limited (e.g. if 1 or 3 point calibration)
 Linearity may “fall off” at high end due to detector
saturation
 Linearity and sensitivity may decrease at low end
due to adsorption to glassware and GC injection
port phenomena
 Important that controls run near upper AND lower
end of reporting ranges if not covered by the
calibrators
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Precision
 Precision is important
– Poor precision means that the “right answer”
may only be obtained some of the time
 Replicate analyses?
– Running samples in duplicate can help to
determine if precision is poor
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Professional Standards
 Professional standards
– Professional Standards should be used as a guide to
“good laboratory practice”
– e.g. SOFT/AAFS Guidelines
 Can help a laboratory get the necessary resources
to meet a nationally or internationally recognized
professional standard
– Useful to convince administrators to provide better
funding (money!)
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Case Study – Inadequate Validation
 The wife of a well-known pathologist died suddenly. He
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was accused or poisoning her with an unknown substance.
Prosecution thought that neuromuscular blocking agents
might be a good possibility
A forensic laboratory developed an LC/MS/MS method for
neuromuscular blocking agents
The laboratory detected succinylmonocholine (SMC) in
the postmortem tissue of the wife of the pathologist
The pathologist was the charged with the murder of his
wife, convicted and sentenced to life in prison
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Succinylcholine (SCC)
 Succinylcholine (SCC) is an unstable ester of two
choline molecules joined to succinic acid
 Because SCC is unstable, a lab can look for the
mono-ester (succinylmonocholine - SMC), but
that is also unstable - but more stable than SCC
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Prosecution Position
 Prosecution toxicologists argued that
hydrolysis of SCC to SMC and eventually
to succinic acid and choline was in one
direction only (not reversible)
 Therefore, they argued that detection of
SMC proved beyond any doubt that the
victim must have been administered SCC
(succinylcholine)
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Defense position
 Defense toxicologists argued that hydrolysis of SCC to
SMC and to succinic acid and choline was an equilibrium,
even though mostly towards complete hydrolysis
 Therefore, since all postmortem tissues contain high
concentrations of succinic acid and choline (NOT from
SCC), therefore combination of these compounds to form
small amounts of SMC was a theoretical possibility
 It was up to prosecution to run adequate negative controls
(postmortem tissues) to prove that trace amounts of SMC
do not exist naturally. They did not do that prior to trial!!
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What was the outcome?
 The jury trial did not take the defense argument
seriously, and convicted the pathologist of
murdering his wife
 Several months later, the laboratory performed the
specificity studies and found that SMC was
formed in postmortem tissues (in cases where
SCC was known NOT to have been given)
 Therefore, there was no scientific evidence that
the pathologist murdered his wife with SCC
 The legal outcome was complex…
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Forensic Toxicology Accreditation
 Several different programs…
 Urine drug testing (workplace testing)
– SAMHSA (U.S. Government - regulatory)
– College of American Pathologists (CAP - voluntary)
 Forensic Toxicology
– American Board of Forensic Toxicology (ABFT voluntary)
 Forensic Science / Police Labs
– American Board of Crime Laboratory Directors – Lab
Accreditation program (ASCLD/LAB)
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What Does Accreditation Cover?
 Administration of the laboratory
 Personnel / staffing / training
 Security and chain of custody
 Procedure manuals / written documentation
– Standard Operating Procedures (SOP)
 Analytical methods
 Quality control / quality assurance
 Reporting of results
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Is Accreditation Mandatory?
 Urine drug testing
– Only for less than 5 – 10% of testing
– Mainly for transportation related jobs
 Forensic Toxicology / Science
– Only in 3 states (New York State, Texas and Oklahoma
– Not at all in Canada
 Ideally, every laboratory should be accredited and
inspected by an accreditation program that is
based on accepted international or national
standards (e.g. ISO 17025; SOFT/AAFS
Guidelines)
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Are All Toxicology Labs Accredited?
 NO!!
 Many labs in Canada and the U.S. have no
accreditation or independent assessment
 The only pressure for labs to become accredited is
“peer pressure”, or a serious mistake that leads to
public or political pressure for accreditation
 There is very little incentive for a lab manager to
seek accreditation of a toxicology laboratory
– It creates more work, with no promise of extra
resources to address staffing and training needs!
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The Future?
 The only way all forensic toxicology laboratories
will adopt adequate and consistent QA standards and become accredited - is if it is mandated by
government legislation (personal opinion!)
 Mandated accreditation can have the benefit of
additional resources in order to meet the
professional standards that have been set
 Standards for forensic toxicology will continue to
become more strict, perhaps following a trend that
already exists for the environmental and
pharmaceutical industries
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Thank you for your attention
and your kind hospitality!
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