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Encyclopedia of Physical Science and Technology EN016H-959 August 1, 2001 11:6

906 Toxicology in Forensic Science

TABLE I Types of Specimens Collected and Their Principal Applications
Specimen Application
Blood (or plasma or serum) Most commonly used for drug detection and is the preferred single specimen for perpetrators and victims of crimes,
death investigation cases, drivers of motor vehicles suspected of drug use
Urine Used in all cases as a screening specimen for drugs of abuse, and is the preferred specimen for workplace,
rehabilitation, and corrections drug testing programs, as well as in sports drug testing programs
Liver and other tissues from Used to supplement blood toxicology in some death investigations, particularly when body is decomposed and when
deceased persons the interpretation of blood results are equivocal
Hair Used when a longer period of drug exposure is required (1–6 months) to complement other information on drug use
a
Sweat and saliva Occasionally used as alternatives to other forms of testing when onsite results are required in workplace and
correctional or rehabilitation settings
Breath Used extensively to establish presence of alcohol in drivers of motor vehicles and in workplace settings
a
Onsite refers to an initial detection of drugs in specimens at the point of collection, rather than waiting for a result from a laboratory.

defending the results in a court of law. This distinction mance testing relates to the detection of drugs that might
from an ordinary analytical toxicologist is important, as a have improved performance in athletic events. This testing
conventional toxicologist is mainly concerned with the de- may even apply to racing animals such as horses, camels,
tection of substances and may not understand the specific dogs, etc. Specimens used in these cases are usually urine,
medico-legal requirements in forensic cases. A forensic although hair is being increasingly used to provide a
toxicologist also is able to assist legal proceedings in the greater window of opportunity in workplace settings.
interpretation of the significance of the results obtained.
II. SPECIMENS
I. APPLICATIONS OF FORENSIC
TOXICOLOGY
A wide variety of specimens can be collected toassess pos-
sible drug use. These include blood (or sometimes plasma
Forensic toxicology has a number of applications. It pro-
or serum ), urine, breath, saliva, sweat in living persons,
∗
vides clinicians with information of a possible drug taken
or a range of other tissues from bodies at autopsy dur-
in overdose or authorities investigating a sudden death or
ing death investigations. In cadavers the most common
poisoning with the possible substances(s) used.
specimens, after blood and urine, are liver, bile, and vit-
Toxicology testing is also important in victims of crime,
reous humour. Muscle, brain, bone, and fat do have uses
or in persons apprehended for a crime. Drugs may have
in certain types of cases when blood is unavailable due
been given by the assailant to reduce consciousness of the
to decomposition or following suspicion of unusual poi-
victim, such as in rape cases. These drugs include the ben-
sons. The principal applications of some specimens are
zodiazepines (e.g., Rohypnol, Valium, Ativan, etc.) and
summarized in Table I.
gamma-hydroxybutyrate (GHB). Toxicology also estab-
lishes if any drug was used by the victim that may have
affected consciousness or behavior. Defendants arrested III. CHAIN OF CUSTODY
shortly after allegedly committing a violent crime may be
under the influence of drugs. Alcohol and drugs are also Courts and other legal processes usually require proof that
commonly targeted in drivers suspected of driving under the laboratory has taken all reasonable precautions against
the influence. unwanted tampering or alteration of the evidence. This ap-
Ultimately, toxicology testing results will assist the in- plies to specimens and to physical exhibits used by the lab-
vestigator, pathologist, coroner, or medical examiner in oratory for toxicology investigations. Consequently, it is
establishing evidence of drug use or refuting the use of essentialthatthecorrectidentifyingdetailsarerecordedon
relevant drugs. This latter application is essential, as few
the exhibit or specimen container and an adequate record
drugs leave any visible trace of their presence in a person.
is kept of persons in possession of the exhibit(s). Alter-
Forensic toxicology is also used in employment drug
natively, when couriers are used to transport exhibits, the
testing, rehabilitation settings, and in human performance
exhibit must be adequately sealed to prevent unauthorized
testing. The detection of drugs of abuse in potential em-
tampering.
ployees prior to being hired is becoming an important ap-
plication of toxicology. Attempts to exclude drugs from
Obtained from blood by either centrifugation to remove red blood
∗
prisons and to aid in rehabilitation of drug-dependent per- cells (plasma) or other types of separation processes to obtain plasma or
sons are other applications of toxicology. Human perfor- serum (fluid obtained after blood has clotted).