help full for knowledge of toxicology

1. Forensic toxicology and
specimen collection

2. Forensic Toxicology
• The application of toxicology for the purposes of
the law.
• Greeks used hemlock as a means of state
sponsored execution. Socrates was the most
famous poisoning case by this method.
• In the U.S., forensic toxicology did not develop
until the early 20th century.
• Dr. Alexander Gettler is considered this country’s
first forensic toxicologist.
• Postmortem forensic toxicology.
• Human performance toxicology.
• Forensic drug testing.

3. Forensic toxicology…
 Drug intoxications are not readily diagnosed at autopsy.
 In IV drug deaths, there may be a recent injection site
observable;
 oral intoxications may be inferred by a large amount of
unabsorbed tablet fragments in the stomach contents.
 Otherwise, the only other anatomic findings are
pulmonary congestion and edema.

4. Forensic toxicology
• the function of the toxicology laboratory is
– to identify the substances present in the biologic specimens.
• Once these substances are identified, they are
quantitated in appropriate specimens to determine
whether these drugs caused or contributed to death.
• Forensic science task is to produce valid toxicological
information for the administration of justice and to
improve the legal protection of individuals and
society.

5. What is Forensic …..?
• As to the analysis of human samples, there
are two key questions:
– Has the person under investigation been exposed
foreign substances
– Has s/he been under the influence of alcohol,
drugs or other xenobiotics.

6. Postmortem Forensic
Toxicology
• Qualitative and quantitative analysis of drugs or poisons
in biological specimens collected at autopsy
– Forensic Pathologist responsible for performing
autopsy.
– Forensic Toxicologist responsible for analyzing
biological samples for poisons
• Interpretation of findings in terms of:
– Physiological effect at time of death
– Behavioural effect at time of death

7. Quantitative vs. Qualitative
• Qualitative analysis – determines the
presence or absence of a drug or poison in a
submitted sample
• Quantitative analysis – determines the
amount of drug or poison that is present in
the submitted sample

8. Postmortem Forensic
Toxicology
Types of cases:
• Suspected drug intoxication cases/Unexplained
deaths
• Arson fire deaths
• Homicides
• Motor vehicle fatalities/Driver and pilot fatalities
• Therapeutic drug monitoring
• Deaths due to natural causes
• Sudden infant death (SIDS)
 Death Investigations
– Coroner
– Medical Examiner

9. POST-MORTEM
TOXICOLOGY
• Analytical results of a post-mortem investigation
are utilized to determine the cause and manner of
death.
• Poisoning can be the:
– Underlying cause of death
• of morbid events leading directly to death
– Immediate cause of death
• with the symptoms of which the deceased
died

10. POST-MORTEM TOXICOLOGY
• Traditionally, the results of a single forensic case are
used for the sake of the deceased in question only.
• Over time, cases accumulate to form a greater whole,
which can provide information that goes far beyond the
original purpose of the routine casework.

11. TYPICAL FEATURES OF FATAL DRUG POISONINGS
• Frequently several drugs are present
• Frequently alcohol has been taken
simultaneously
• Frequently the victim has committed suicide
• Drugs of abuse are common
• Victims include young people also

12. THE MOST IMPORTANT
FINDING
• A combination of several drugs is typically found in
the same subject.
– If all findings are included in the classification,
the number of possible fatal combinations is too
high.
– The forensic pathologist always has a possibility to
choose the most important finding.
– If not stated, the drug which has the greatest
ratio of found concentration in relation to its
therapeutic concentration is taken as the basis of

13. 13
Areas of Application
• Postmortem drug testing –
– this is used in death investigations to establish whether
or not drugs were the cause or contributing factor in
death.
• Workplace drug testing –
– this consist of evaluation of biofluids, primarily urine
and blood from employees or job applicants for drug
content.
• Evaluation of Contraband –
– this is applied when evidence seized is being linked to

14. 14
Analytical Methods in Forensic Toxicology
• is important as the types of fluids that are tested.
• A good working relationship between death
investigators and laboratories is essential in success
of solving death investigations.
• Remember, death investigation is a team effort and
toxicology is a vital member of the team.

15. Analytical Methods ,,,,,
• Lab Expected to Provide
– Identification of agents/toxicant/ for poisoning
– Detection of drug abuse,i.e.in the victim blood.
– Therapeutic drug monitoring/for low TI drugs-w/c
are potentialy toxic/=TDM
• No- of cpds for which true emergency lab results are
needed to guide therapy are few
• For most, victims are treated empirically before lab
results are known

16. Analytical methods in (cont.)
• Information necessary for the lab="SATS"
– Suspected agent/substance
– Suspected amount
– Time of ingestion and sampling
– Clinical presentation
– Location of victim-where the exposure happens
• gives us information to assess more and how
the poisoning happens.
• to interview others who don’t come to clinics
while still poisoned.

17. Types of Specimen
• Urine
• gastric contents
• Blood
• bile
• CSF
• Vitreous Humor
• hair
• Nonbiologicals (scene residues)- staffs near the
victim where the poisoning occurs,OTC
medication,left over medication,empty bottles,,,,

18. Choice of Specimen
• Depends on
– Kinetics of the suspected agent
• For not absorbable agent/polar substance/: GI
specimen
• For absorbable agent/non polar toxicant/:
blood specimen
– Lab method
• For qualitative test: urine specimen/gastric
contents
• For quantitative tests: serum/whole blood
specimen

19. Specimen Collection
• Selection
– Multiple, varied sites of collection
• Collection
– Appropriate method of collection
– Adequate volumes for analysis
• Storage and handling
–Important to ensure analytical results are accurate
and interpretations are sound

20. 20
Specimen Collection
Blood
– the most satisfactory method for obtaining samples is
from venous puncture of the femoral vein.
– An alternate site to collect venous blood is to incise
the jugular.
– To be collected in sealed heparinized tube
– Could be whole blood, plasma, serum
– this is typically done after the neck has been exposed
under the sub-clavicular incision.
– The correlation between blood concentration and
effects of the drug is very high in blood testing.

21. 21
Specimen Collection
Urine
• is most often used to test for presence of drugs: because of the
types of test that can be run and the cost effectiveness of the
testing.
– Simple for collection
– 50ml to be collected
– Higher conc. of chemicals available and
• draw back:
– the correlation between drug concentration in urine and drug
effects is usually poor.
• Urine should also be collected in post mortem investigations since
some toxins show in higher levels in urine.

22. 22
Specimen Collection
Bile
• Because bile drains from the liver it is often times
very rich in certain types of drugs such as opiates.
• These toxins are concentrated by the liver and
excreted into the gall bladder.
• this can be useful in cases where morphine and
chlorpromazine are suspected toxins.
• Direct collection of bile into a bottle is advised
because bile is too viscous to be sucked through a
needle.

23. 23
Specimen Collection
Cerebrospinal Fluid
• not often collected for toxins, but may be needed
for microbiological analysis.
• If needed it should be collected by lumbar or
cisternal puncture.
– Cisternal puncture = Passage of a hollow needle
through the posterior anto-occipital membrane
into the cerebellomedullary cistern

24. 24
Specimen Collection
Vitreous Humor
• The fluid found in the center of the eye is the vitreous
humor.
• sometimes useful in bodies with appreciable post mortem
decay.
• The fluid in the eye resist putrefaction longer than other
body fluids.
• This is especially handy in a case in which there has been
a great deal of decomposition since vitreous humor may
be the only fluid still available to test.
• Vitreous can also be used at estimating time of death.

25. Collection of Specimens
gastric Contents
• Includes vomit, gastric aspirate, stomach wash (1st
sample/portion/ of washing)
• 20ml to be collected; Gives clue by smell
• Capsules or tablets to be identified by physical
inspection in the vomit
• is typically done in a sudden death in which the
decedent has large quantities of a lethal agent in his
stomach.
• Contents should be emptied into a wide mouth jar.
• In the case of suicide, large amounts of toxins in the
gastric tract may make this point apparent.

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Specimen Collection
• Hair
– Not common in forensics for a number of
reasons.
–Drugs only present in extremely low
concentrations.
–Controversy between active and passive
drug usage arise.
–The benefit of hair is that its is a good
timeline for drug usage since it is only
eliminated when hair is cut.

27. Collection of Specimens (Cont.)
Nonbiologicals (scene residues)
• Few mg is sufficient
• Sufficient amount need to be conserved
for further analysis
N.B. all should be collected before any
chemical admn./including drug/-b/c may
complicate the analysis and give false +ve
/-ve result.
soln.:-Therefore, after maintaining the
ABCD/supportive therapy/ you could take
specimen prior to adminstering drug for
symptomatic therapy.

28. Transport and /Storage of Specimen
• Need proper labeling-prior to transport.
• Organic solvent to be packed separate
from biological specimens to avoid cross
contamination-while transporting.
• All biological specimens to be stored at 4C°
• Some left over to be stored for medico-
legal purpose

29. Examination of Specimens
a. Physical Examination
I. Urine
• Color change: iron+deferroxamine=red
• Smell: methylsalicylate+reagent=strong
smell
• Appearance:
carbonates+reagent=turbidity
II. Stomach Contents
 Smell: alcohol smell, garlic smell
 pH:
 basic toxicants = high
 Acidic toxicants= low

30. Analytical methods in ...
• Spot tests: color change in urine/blood with
specific reagent
• UV spectroscopy: barbiturates
• Immunoassay: recognition by specific
antibodies (Abs) (opioids)
• Chromatography: TLC, GC ( for volatile cpds),
HPLC (for nonvolatile Cpds)
• Mass spectroscopy: almost for all(either
volatile or not)
• Nuclear magnetic resonance (NMR): most
sensitive(i.e, even to very small amt of
substance) but expensive

31. Analytic methods…

32. Human Performance Toxicology
• This branch of forensic toxicology is concerned with
the relationship between the presence of a drug and
associated behavioral changes.
• It is generally accepted that there is a dose-effect
relationship between drugs that elicit behavioral
changes and those changes;
• elucidation and quantification of such a relationship is a
significant role of the behavioral toxicologist.
• Human performance toxicology is also referred to as
behavioral toxicology.
– E.g Ethanol and driving

33. Breath Ethanol Testing
 Chemical
• Reaction of ethanol with potassium
dichromate/sulfuric acid solution
• Oxidation reaction with a color change from yellow
(dichromate ion) to green (chromic ion)
 IR Spectrophotometry
• Based on absorbance of light by the ethanol molecule
• Mainstay in evidential breath testing devices
 Electrochemical Oxidation
• Oxidation of ethanol to acetic acid
• Also used in evidential breath testing

34. Immunoassay
• Has the ability to
determine small
concentrations of drugs
in body fluids and
organs
• Best approach for
detecting low drug
levels in body
• Usually used for
marijuana screening

35. Color Tests
• Most drugs react with certain
chemicals to produce a specific
color
• Marquis: purple in heroine, opium.
Orange brown in
(meth)amphetamines
• Dilli-Kopanyi: violet in
barbiturates
• Duquenois-Levine: purple for
marijuana
• Van Urk: blue purple in LSD
• Scott test: blue, pink and blue

36. Microcrystalline tests
• A small drop of a
chemical is added to a
small amount of drug
which forms a crystalline
structure
• Size and shape of crystal
can be used to identify
drug

37. Spectrophotometry
• Identifies drug on based on
the type of light it absorbs
• Infraredspectrophotometry
can identify a specific drug
because infrared spectrum
is unique for all drugs
• Other types of
spectrophotometry are
sometimes inconclusive

38. Steps in Toxicological Analysis
1.Preanalytic Phase: Victim’s history and Physical
examination
2. Analytic Phase: Toxicological analysis-analysing the
subs. using the previous methods.
3. Post-analytic phase: Results’ interpretation /as to
come to conclusion/;
• Repeating analysis if need be

39. 39
Interpreting Findings
• Workplace drug testing is usually conducted for the
purpose of answering one of two questions
• History of drug use for hiring purposes
or
• explanation of erratic behavior of current employee.

40. 40
Interpreting Findings
• The goal of a forensic toxicologist is to confer with
the pathologist in determining the cause and manner
of death.
• In simple terms we infer that the death is due to a
specific toxin when appropriate quantities of that
toxin are found.
• When other findings conclude cause of death we may
specify the toxin as a contributing factor to death.