Unit 2 – Lecture 7
Forensic Toxicology
Classification of Poisons
Prof. Dr. P.T. Jayaprakash PhD
Formerly: Assistant Director, Forensic Sciences Department; Professor, Forensic
Sciences, University of Madras and Associate Professor, Forensic Science
Program, School of Health Sciences, Universiti Sains Malaysia
Prof. Dr. P.T. Jayaprakash, MSc Crim, 03.10.2023 Chennai
Toxicology
Definition: Toxicology is the science of poisons which
is applied to medico-legal proceedings
Toxicologist: A forensic toxicologist is concerned
with the detection of drugs or poisons in samples and
is capable of defending the result in a court of law.
Poison: A substance producing ill effect or death
when administered in any manner.
Prof. Dr. P.T. Jayaprakash, MSc Crim, 03.10.2023 Chennai
Applications of Forensic Toxicology
In death investigation: Traditionally, it is used in death
investigations. It provides post-mortem doctor with
information of a possible drug taken while alive.
In drug administered cases: Drugs may have been given
by the assailant to reduce consciousness of the victim,
such as in rape cases. These drugs include the
benzodiazepines (sleeping pills).
In drug abuse cases: The substances that are abused are
tested and certified.
In enhancing performance in sports: In cases in which
drugs are administered for increasing performance in
sports and by athletes.
Prof. Dr. P.T. Jayaprakash, MSc Crim, 03.10.2023 Chennai
Manners of administration or routes of administration
(routes of entry into thew body):
External (normal) routes:
Oral or rectal or vaginal: through the mouth, anus or
vagina
Parenteral route:
Through injections: intravenous or intra muscular or
subcutaneous, cardiac or spinal injection
Through inhalation: when respiring
Through the skin: when contacting the skin
Prof. Dr. P.T. Jayaprakash, MSc Crim, 03.10.2023 Chennai
Elimination of poisons
Major routes of exit of products of poisons from the
body are via
Urine
Faeces
Excretion from skin (sweat)
Brest milk
Vomitus
Other mucus secretions
Thus, urine, faeces and vomitus form useful evidence
for detecting poisons during investigation
Prof. Dr. P.T. Jayaprakash, MSc Crim, 03.10.2023 Chennai
CLASSIFICATION OF POISONS
I. IRRITANT POISONS
Irritant poisons are those which, by their specific action, set up
inflammation In the gastro-intestinal canal.
Non-metallic: Phosphorus
Metallic: Compounds of Arsenic, Mercury, Lead
Acids: Hydrochloric acid, Sulfuric acid
Others: Kerosene
Prof. Dr. P.T. Jayaprakash, MSc Crim, 03.10.2023 Chennai
II. INORGANIC COMPOUNDS – these are salts - contain two
molecules
Potassium cyanide: Usually termed ‘King of poisons’ –
White crystalline powder - Produces hydrocyanic acid
(HCN) in the stomach
HCN inhibits cytochrome oxidase activity and thus
prevents release of oxygen from hemoglobin to the
cells and organs – the person dies of lack of oxygen
Death is immediate – cyanide capsules used by
extremists to commit suicide when caught by police
Arsenic sulphide: Called ‘Realgar’ – a soft mineral
Chronic poisoning – high level found in the hairs
samples of Napoleon Bonaparte – there is a theory that
he was administered slow doses of arsenic – but this is
not supported
Prof. Dr. P.T. Jayaprakash, MSc Crim, 03.10.2023 Chennai
III. AGRICULTURAL CHEMICALS (PESTICIDES)
These chemicals called ‘pesticides’ are used to kill or control
pests.
Insecticide of different types
Type: BHC (gammaxene) – the ant killing powder
Type: Organophosphorus – Malathion, Parathion (Folidol)
Type: Carbamate – Carbaryl
Organophosphorus and carbamates are systemic insecticides.
both inhibit cholinesterase activity – neuro-muscular junction -
cause tetanus (fits) leading to death
IV. PLANT TOXINS:
Oleander (Tamil: Arali)
Datura (Tamil: Oomathai) Strychnine
V. ANIMAL POISONS: Snake venom, Scorpion venom
Prof. Dr. P.T. Jayaprakash, MSc Crim, 03.10.2023 Chennai
Organs useful for detecting poisons
During postmortem examination, the doctor preserves
samples of organs for detecting poisons by the Forensic
Science Laboratory.
Stomach: the poison that is not yet absorbed is detected
as such (this poison has not caused the poisonous
effects on the body!!!)
Intestine: Partially metabolized poisons
Liver: Partially metabolized poisons
Kidney: Partially metabolized poisons
Skin: Local corrosives
Prof. Dr. P.T. Jayaprakash, MSc Crim, 03.10.2023 Chennai
Collection of evidence from a scene of poisoning
Spilled poison or container (glass tumbler etc.)
stained with poisons
Vomit, saliva, faeces
In case of exhumation of a body, soil from below the
body to be collected along with control earth
Viscera samples such as stomach, intestine, liver,
spleen and kidney from the dead body collected
during postmortem examination
Clothing of the suspect in case of suspected
homicide
Prof. Dr. P.T. Jayaprakash, MSc Crim, 03.10.2023 Chennai
DEATHS DUE TO POISONING
All manners of death are known in poisoning—it could be any one
of the three types, viz. suicidal, accidental, or homicidal.
CAUSE OF DEATH DEMONSTRABLE: The fact that death was due
to poisoning is invariably demonstrable due to the regular autopsy
practice of preserving the visceral organs for toxicological
analysis in every case of suspicious death and the advanced
analytical abilities presently available in forensic science
laboratories to detect toxic substances.
When the victim’s dead body is available in a scene of poisoning,
and the manner of death is suicidal, there are telltale evidence—
mostly those indicating deliberate ingestion of the poison—
observable in the scene itself supporting the hypothesis of
suicidal poisoning.
In cases where the victim is taken to the hospital for treatment, the
history relating to the symptoms recorded in the hospital and the
treatment given to the victim would help in supporting the manner
of poisoning.
Prof. Dr. P.T. Jayaprakash, MSc Crim, 03.10.2023 Chennai
Poisoning in relation to homicide:
It can be of two broad types—
one in which the victim dies due to clandestine
administration of a poison that is consumed unknowingly
and
the other in which the victim is killed by some other means
such as throttling, and poisoning is staged in the scene.
In the former type, poison would be detected in the stomach
content, while in the latter category, poison may not be
responsible for the death and thus may not be detected in
the organs.
In both the cases, the crime scene findings would play an
important role in supporting the hypothesis on the manner
of death.
Prof. Dr. P.T. Jayaprakash, MSc Crim, 03.10.2023 Chennai
DEATH DUE TO POISONING—SUICIDE, ACCIDENT, OR HOMICIDE
THE CASE
A female individual reportedly committed suicide in her house by
consuming insecticide.
The deceased was found laid
on a bench.
Drained tracks of darkly
stained substance were
observable on both the sides
of the mouth of the deceased.
Prof. Dr. P.T. Jayaprakash, MSc Crim, 03.10.2023 Chennai
In the place of occurrence, the kitchen part of the
house, there was evidence of darkly stained vomited
matter on an improvised mat (arrows in Figure).
Prof. Dr. P.T. Jayaprakash, MSc Crim, 03.10.2023 Chennai
A container of organophosphorous insecticide was
found in the nearby empty country oven (Figure).
Prof. Dr. P.T. Jayaprakash, MSc Crim, 03.10.2023 Chennai
PRIMARY HYPOTHESIS
The victim died due to poisoning, and the manner was suicide.
ALTERNATIVE HYPOTHESIS 1
The victim died due to poisoning, and the manner was accident.
ALTERNATIVE HYPOTHESIS 2
The victim died due to poisoning, and the manner was homicide.
Prof. Dr. P.T. Jayaprakash, MSc Crim, 03.10.2023 Chennai
SEQUENTIAL HYPOTHESIS 1
Evidence of vomiting in the scene
supports deliberate ingestion of
the poison.
Observed premises
Dried tracks of darkly stained
material were seen on both the
sides of the mouth of the deceased
(Figure).
Similar darkly stained materials
were found on different places on
the sheet of polythene spread out
for use as an improvised mat
(arrows in Figure) on the kitchen
part of the house.
Prof. Dr. P.T. Jayaprakash, MSc Crim, 03.10.2023 Chennai
Accepted (major) premises
Evidence of vomiting in the scene indicated an acute effect of the
insecticide that is consumed in copious amount. Deliberate
ingestion of insecticide is indicated among adults exhibiting acute
symptoms such as vomiting (Ferreira et al., 2008).
Reconstruction
The evidence of vomiting, an acute effect the poison on the victim,
supports deliberate intent on the part of the deceased in
consuming copious amount of the insecticide and in abstaining
from seeking first aid which support suicidal intent.
Prof. Dr. P.T. Jayaprakash, MSc Crim, 03.10.2023 Chennai
SEQUENTIAL HYPOTHESIS 2
Organophosphate insecticides are not suitable for unaware or
unnoticed administration with homicidal intent.
Observed premises
An appropriately labelled container of organophosphorous
insecticide with residual insecticide was found in the empty country
oven (Figure) in the scene hut.
Accepted (major) premises
Containers of insecticides are
suitably labeled and hence are
readily recognizable. Furthermore,
poisons of organophosphate types
have characteristic pungent odor
and thus are neither likely to be
consumed accidentally nor suitable
for unnoticed administration with
homicidal intent.
Prof. Dr. P.T. Jayaprakash, MSc Crim, 03.10.2023 Chennai
Reconstruction
The presence of the insecticide container with
recognizable label in the scene supports the inference that
the deceased had consumed the insecticide deliberately.
The fact that organophosphate insecticides have
characteristic pungent odor that is readily detectable
further supports voluntary ingestion rather than accidental
intake or clandestine administration by another individual.
Prof. Dr. P.T. Jayaprakash, MSc Crim, 03.10.2023 Chennai
Conjoined reconstruction
Voluntariness and intent on the part of the deceased in
consuming the insecticide are indicated by the evidence of
vomiting, an acute effect of the poison as well as the presence
of the insecticide container in the scene.
The deceased, an adult, had abstained from seeking first aid, an
act that does not support accidental poisoning.
Homicidal poisoning by clandestine administration by another
individual is not supported since organophosphate insecticides
have readily recognizable pungent odor.
Thus, sequential hypotheses 1 and 2 support the primary
hypothesis that death was due to poisoning and that the manner
was suicide.
During autopsy, the samples of visceral organs were preserved,
and analysis in the Forensic Science Laboratory indicated the
presence of organophosphate compound in the organs.
Prof. Dr. P.T. Jayaprakash, MSc Crim, 03.10.2023 Chennai
Myths and Facts Relating to Observations in Death due to Poisoning
i. Myth: Aerosols and solids in the form of powders that come into
contact with the skin when spraying insecticides can be washed
off and hence are not harmful.
Fact: While solids in the form of powders do not penetrate the skin,
liquid insecticides used as aerosols penetrate the skin causing
toxic effects.
ii. Myth: The quantity of the poison that is consumed can be
detected by analyzing the stomach content.
Fact: The quantity of poison detected in the stomach is the
unreacted portion which remains after the quantity that has been
absorbed into the system.
Prof. Dr. P.T. Jayaprakash, MSc Crim, 03.10.2023 Chennai
iii. Myth: It is possible to clandestinely administer commercially
available insecticides for homicidal purposes.
Fact: Insecticides available in the markets are characterized by
varying colors and pungent smell and hence are easily
recognizable due to their repulsive smell. It is usually not possible
to administer such poisons unknowingly.
iv. Myth: Treatment has proved to be more successful in saving
victims who had consumed poisons accidentally.
Fact: True. This is mainly because of the fact that the poison
consumed, when accidental, gets restricted once the victim
becomes aware of it. Consequent to this awareness, the initiation
of treatment is immediate leading to saving the victim. In addition,
the poisons accidentally consumed are such that they are generally
less strong such as kerosene unlike the insecticides that produce
acute effects.
Prof. Dr. P.T. Jayaprakash, MSc Crim, 03.10.2023 Chennai
Toxicology related samples and analysis
Material Packing/Forwar Control Type of
Evidence ding Procedure Material Examinatio
n/ Analysis
Viscera Glass bottles – Materials collected from SOC like To detect
Stomach and 500 ml Vomitus the poison /
contents capacity with Purges drug.
Intestine and plastic Remnant poison
contents screw caps. Remnant food and the vessels,
Liver Preservative*: plates etc., including fruits / Empty
Kidney Saturated poison containers
Brain saline tablets, injection vials, syringes,
needles, tablet strips etc.,
Clothing with vomitus
a) For Preservative - do - - do -
detecting desired:
corrosive Rectified spirit
poisons. instead of
saturated
saline.
b) For Preservative - do - - do -
detecting plant desired:
poisons Rectified spirit
with 2% acetic
acid.
Prof. Dr. P.T. Jayaprakash, MSc Crim, 03.10.2023 Chennai
Material Evidence Packing/Forwardi Control Type of
ng Procedure Material Examinatio
n/ Analysis
c) *For detecting and Preservative - do - - do -
estimating the drugs. desired:
Additional samples: Sodium citrate for
Blood and Urine blood and
mercuric chloride
for urine.
d) *For detecting metal Pack as such in - do - - do -
poisons (Chronic). paper /
Additional samples: cardboard parcel
Hairs, nails and long bones with out any
with marrow. preservative.
e) *For detecting injected (IV For blood and - do - - do -
/ IM etc.,) poisons / drugs. urine preserve
Additional samples: properly.
Blood, urine and skin/tissue Tissues to be
from site of injection (skin pickled with solid
bit). sodium chloride
(common salt).
Prof. Dr. P.T. Jayaprakash, MSc Crim, 03.10.2023 Chennai
Interpretation of Toxicological Results - complexities
Consideration must be given to the circumstances of the
case. For example, the finding of a drug in potentially toxic
concentrations in a person killed by a gunshot wound to the
head cannot reasonably lead to the conclusion that drugs
caused the death.
Consider example of cyanide in a person with gun shot
travelling along his lungs.
On the other hand, the absence of an obvious anatomical
cause of death will lead investigators to consider the role of
any toxin use.
Considerations must include interpretation of the residual
toxin in stomach as well as the metabolites in the organs like
liver.
Prof. Dr. P.T. Jayaprakash, MSc Crim, 03.10.2023 Chennai
