Written by A. Wayne Jones, Jørg G. Morland, and Ray H. Liu
An excerpt from: Alcohol, Drugs, and Impaired Driving: Forensic Science and Law Enforcement
HANDHELD INSTRUMENTS for the determination of ethanol in breath have been used by the
police to control sobriety since the early 1970s (Poon et al. 1987). Likewise, instruments suitable for
evidential purposes have gone through
six generations since the Breathalyzer was invented in 1954 (Wigmore
& Langille 2009). The analytical
principles for quantitative analysis of ethanol in breath
either involve electrochemical oxidation with a fuel-cell sensor or infrared
spectrometry; some devices incorporate both technologies (EC and IR) to enhance
selectivity for identifying ethanol (Jones 2000). The accuracy and precision of
modern breath-alcohol instruments matches that of GC analysis of ethanol in blood.
The gold standard method of blood-alcohol analysis involves the use of headspace gas chromatography with flame ionization
detector (HS-GC-FID) or, more
recently, a mass detector (HS-GC-MS) (Tiscione et al. 2011). This type of methodology has been used for legal
purposes since the 1960s and gives accurate, precise, and specific results fit
for its intended purpose (Jones 1996).
major historical developments in the analytical methods used for determination
of ethanol and other drugs in biological specimens for clinical and forensic
Table 1. Historical Landmarks in the Development of Methods for
Analysis of Alcohol and Other Drugs in Biological Specimens for Legal Purposes
The quantitative analysis of drugs other than ethanol
is a more challenging task for analytical
toxicologists for several reasons. First, as stated earlier, the
concentrations of non- alcohol drugs
in blood and other biological fluids (see Table 2) are 1,000–10,000 times lower than concentrations of ethanol. Second,
ethanol is easily separated from the biological
matrix by its volatility, whereas other drugs need to be extracted with
organic solvents or solid-phase cartridges, which is more troublesome and costly (Maurer
Table 2. The Mean, Median, and
Highest Concentrations of Ethanol and Other Drugs Identified in Blood Samples
from Motorists Apprehended in Sweden—The Results Represent Data Accumulated
Over Several Years During the Period 2000–2012
The pharmacologically active substance is first extracted
from blood or tissue by adjusting
the pH so that drug molecules are in their unionized form and therefore
more lipophilic. The buffered
mixture is then shaken with organic
solvents or added to specially designed solid-phase columns. In this way,
the active drug is separated
from interfering substance and/or any drug metabolites
prior to analysis by GC or LC using various detector systems, such as flame
ionization detector, electron capture detector, nitrogen-phosphorous detector, or a mass detector (MS) with selected ion monitoring (Maurer
important advance occurred when capillary column GC methods appeared in the
1980s, which improved sensitivity and specificity of the assay considerably.
The time elapsed after injecting the
sample onto the GC column to the
time of appearance of a peak is known as the retention time (RT) and serves to
identify the analyte (qualitative
analysis) by comparing RT with known authentic substances.
Alternatively, relative retention time (RRT) is another way of identification,
whereby the time for elution of the GC peak is compared with RT of an
internal standard added to the biological specimen before analysis
(Mbughuni et al. 2016). When GC-MS or LC-MS methods of
analysis are used, it is customary to make use of deuterium-labeled internal
standards and both RT and mass
fragmentation patterns help to identify the drugs and/or metabolites in the
sample (Maurer 1992).
Today’s analytical methodology for the determination of drugs in biological specimens is highly sophisticated, fully automated, and controlled by computer
systems and workstations. Separation
methods based on GC or LC are first and foremost coupled with mass-selective
detectors, often high-resolution instruments—so-called tandem detectors GC-MS-MS
or LC-MS-MS (Maurer
and Meyer 2016; Meyer et al. 2016). The positive
identification of hundreds of psychoactive substances and their metabolites is
no longer a difficult task for analytical toxicologists.
However, the correct interpretation
of the analytical results is more
challenging, especially when compliance with some threshold concentration limit
is an issue in criminal prosecutions. In this connection,
making an allowance for uncertainty by
subtracting a certain amount from the analytical
result is highly recommended when concentration per se statutes are enforced (Kristoffersen et al. 2016)
as is commonly done with forensic BAC
determinations (Gullberg 2012). Neither
should one forget pre-analytical factors,
such as those
associated with sampling,
transport, storage, and chain-of-custody issues as well as stability of
the target drug during storage (Kouri
et al. 2005).
of Analytical Results
absorption into the bloodstream, drugs are transported to the brain and
interact or bind with certain receptor sites and proteins causing impairment of
thought processes, and altered performance and behavior, etc. The degree
of impairment associated with drug use depends on the type of drug,
the mechanism of action, the dose taken, and the time after intake when
driving occurs. Drugs are eliminated from the body by metabolism and excretion at widely different rates, varying from a few hours
to several days, depending on the drug’s elimination half-life.
toxicology results are interpreted in DUID cases, it is important to consider
the entire case scenario. This includes observations about the driving, results
of field sobriety tests if any, clinical signs and symptoms, and the DRE
examination results along with the toxicology report. The totality of
information available allows reaching an evidence-based opinion about
impairment caused by drug use and whether the concentrations in blood are
consistent with therapeutic usage or overdosing with medication (Launianinen
and Ojanpera 2014). The question of whether a patient was compliant (or not)
with their medication can be gleaned by comparison with therapeutic
drug-monitoring programs and concentrations of the same drugs in plasma or
serum (Jones et al. 2007).
on knowledge of the main pharmacokinetic parameters of the drug (such as
distribution volume, elimination-rate constant, and half-life), tentative
conclusions can be drawn about the amount of drug in the body and sometimes
when it was taken in relation to driving (Huestis et al 2005). The
concentrations of drugs in blood, plasma, or serum are more closely related to
amounts reaching the brain and the pharmacologic response, including impairment
of body functions (Nedahl et al 2019).
is an excellent specimen for a preliminary screening analysis and also provides
a wider window of detection compared with blood or plasma; but urinary
concentrations cannot be used to draw inferences about concentrations existing
in blood nor any drug-related effects on impairment (Liu 1992). Positive
results from the analysis of urine verifies prior usage; however, calculating
the dose administered or the time of last intake is not possible with any
degree of scientific certainty.
field of forensic toxicology, drugs are almost always determined in blood,
whereas clinical laboratories (dealing with therapeutic drug monitoring) analyze the
concentrations in plasma or serum. The concentrations of drugs in these
biological media are not necessarily the same, depending on lipid- to
water-solubility and the amount of binding to plasma proteins and other
biomolecules (Jantos et al. 2011). In general, drug concentrations in plasma/serum are higher than in an
equal volume of blood. These distribution ratios should be considered when analytical
results from forensic
laboratories are interpreted
and compared with therapeutic concentration in clinical pharmacology. Some
examples of serum/blood distribution ratios for drugs determined in blood of
drivers are 1.7–2.0 for THC (Gronewold & Skopp 2011), 1.6–1.8
for diazepam (Jones Larsson 2004), and 1.01–1.15 for various alcohols, such as ethanol
(Skopp et al. 2005).
AW Jones was
born in Wales, UK, but has lived and worked in Sweden for over 40 years. He
recently retired from his appointment as senior scientist at Sweden's National
Laboratory of Forensic Medicine, Division of Forensic Genetics and Forensic
Toxicology (Linköping, Sweden). Jones currently serves as a guest Professor in
Forensic Toxicology at the Department of Clinical Pharmacology, University of
Jørg G. Mørland received
an M.D. degree from the University of Oslo in 1967 and a Ph.D. degree in
pharmacology from the same university in 1975. Mørland is now a senior
scientist at the Division of Health Data and Digitalization of the Norwegian
Institute of Public Health and a professor emeritus at the University of Oslo.
Ray Liu took
a degree in law from the police academy (now Central Police University) in
Taipei, Taiwan before coming to Indiana University (Bloomington, Indiana) to
study forensic science under the guidance of Professor Robert F. Borkenstein
with internship training in Dr. Doug Lucas’s laboratory (Centre of Forensic
Sciences in Toronto, Canada). He then studied towards a Ph.D. degree in the
Department of Chemistry, Southern Illinois University (Carbondale, Illinois),
which was awarded in 1976.
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