FORENSIC TOXICOLOGY


Definition
  • Toxicology-science dealing with properties,actions,toxicity ,fatal dose,detection,estimation of and the interpretation of result of toxicological analysis and treatment of poisons
  • Forensic toxicology deals with medical and legal aspects of harmful aspects of chemicals on human beings
  • Poison is a substance (solid,liquid or gas)which if introduced into the living body,or brought into contact with any part thereof,will produce ill health or death,by its constitutional or local effect or both.


CORRHOSIVE

  • Strong acid
  • Strong alkali

IRRITANT

1.Inorganic:
  • Non-metallic-phosphoros, chlorine, bromine
  • Metallic- arsenic, mercury, lead, zinc, copper

2.Organic:
  • Vegetable- castor seed, croton oil, aloe
  • Animal- snake bite, insect bite, cantharides

3.Mechanical:
  • Diamond dust
  • Powdered glass

SYSTEMIC

1.Cerebral:

  • Somniferant- opium and other alkaloid
  • Inibriant- alcohol, ether, chloroform
  • Deliriant- dhatura, balladona, cannabis

2.Spinal: nuxvomice
3.Cardiac: digitalis, tobacco, aconite
4.Asphyxiant: war gas, coal gas, sui gas
5.Peripheral: curare

Symptom characteristic of a particular poison
  • Violent convulsant
  • Quick death
  • Hallucination and delusion
  • Drowsiness
  • Colic and pronounced diarrhoea
  • Paralysis ,unconsciousness
  • Coffee brown vomitus with garlic odour
  • Bluish green vomitus
  • Black vomitus
  • Yellow vomitus
  • Strychinine
  • Cyanide
  • Dhatura or atropine
  • Opium, tranquiliser, hypnotic
  • Arsenic, lead
  • Carbolic acid, nicotine
  • Phosphorus,
  • Cuso4
  • Sulphuric acid
  • Nitric acid, chromic acid

Treatment of poisoning

1.Stop further administration

2.Removal of unabsorbed poison
  • Emesis
  • Gastric aspiration and lavage
  • Whole gut lavage
3.Check further absorption with antidote

  • Mechanical or physical example- oil, fat, milk, banana
  • Chemical- to neutralize poison, e.g. weak acid, weak alkali
  • Universal antidote like activated charcoal, milk of magnesia, tannic acid


4.Prevent further action of absorbed poison with chelating agent
  • BAL (Bristish, Anti-Lewisite for heavy metal poisoning)
  • EDTA for lead
  • Penicillamin for copper, lead and mercury
  • Dicobalt edetate for cyanide
  • Desferrioxamine for iron
5.Elimination of absorbed poison

  • Diuresis,
  • Sweating
  • Dialysis
  • Hemoperfusion, exchange transfusion
6.Treat general symptoms

CORRHOSIVE- H2SO4, HNO3, HCl, oxalic acid, acetic acid, caustic potas, NH4CO3

Suicidal ingestion of a corrosive substance (Lysol). Spillage around the mouth has run down the neck and onto the chest.

  • The symptoms are obvious and immediate, with pain at the sites of exposure, usually the mouth and on the skin, difficulty in swallowing, chest pain, abdominal pain, vomiting, difficulty in breathing, choking.
  • If the amount ingested is significant, there will be signs of shock, with collapse, a weak and rapid pulse, hypotension and possibly death, even if treatment is available straightaway.
  • Avoid gastric lavage

Sulphuric acid:

  • Colorless, oily liquid, damages the tissue by dehydration
  • Signs and symptoms- burning pain in mouth, throat down to stomach, nausea, vomiting, dark brown or black vomitus mixed with blood, chalky white teeth, swollen or excoriated lips, difficulty breathing if larynx involved, weakness and collapse
  • Treatment with- neutralisation with milk of magnesia, milk or lime water, analgesia for pain, corticosteroid, fluid replacement
  • Gastric lavage is contraindicated
  • Fatal dose- 10-15 ml, fatal period is 12-24 hours.
  • MLI- used for suicide, mostly accidental, abortificent,vitriolage(throwing acid)
  • Cause of death-circulatory collapse,spasm or oedema of glottis,collapse d/t perforation of stomach

Nitric acid/Aqua Fortis:

  • Yellowish liquid, choking odor, colorless irritating fumes on exposure to air
  • S/S- like H2SO4 except tissues stained yellow, abdominal distension due to gas formation, lacrimation and conjunctivitis, death may occur d/t pulmonary edema.
  • MLI- used for suicide, accidental, homicidal (rare).
  • Fatal dose- 15-20 ml, fatal period- 12-24 hours.

HCl / Muriatic acid:
  • Pungent, colourless fuming liquid, less corrosive ,is in stomach. destroys mucosa.
  • S/S- as H2SO4, HNO3 but milder & more respiratory symptoms being volatile
  • PM findings- skin and mucus membrane whitened, ashy grey or black; errosive esophagitis; stomach is red, perforation is less common.
  • Fatal dose- 15-30 ml, fatal period is 18-30 hours.



Oxalic acid:

  • Although not as corrosive as the mineral acids, oxalic acid and potassium quadroxalate are very toxic, death often occurring within a hour or so if the solid or concentrated solution is taken.
  • They are used extensively as bleach for stain removal and in many other trades and industries .
  • Natural constituent of many plants e.g.spinach,cabbage
  • Colorless, prismatic crystals, rapid poison
  • S/S- sour taste, burning in throat, stomach
  • rarely damage skin but readily corrode the mucosa;
  • purging & tenesmus; stools contain blood; low BP; skin cold & clammy
  • Treatment- give chalk in water; gastric lavage; gastric purgatives; i/v calcium gluconate and calcium chloride(antidote of any oxalate is calcium which binds and forms,calcium oxalate); i/m morphine for pain; inj. coramine to elevate BP
  • Fatal dose- 15 gms, fatal period is 1-2 hours.


Carbolic acid/ phenol:
  • Long, colorless, prismatic needle shaped crystal
  • Largely used as antiseptic and disfectant
  • Turns pink on exposure to light and air, intense penetrating odour
  • S/S- hot burning sensation from mouth to stomach, corroded lip, mouth, tongue; nausea, vomiting; pulse small, BP low; greenish appearance of urine k/a carboluria; death from respiratory paralysis as phenol is a respiratory depressant.
  • T/t- milk, vegetable oil or any demulcent; stomach wash; inj. morphine for pain; artificial respiration for shock; antibiotic prophylaxis of pneumonia
  • Fatal dose- 15 gms, fatal period is 3-4 hours.

Aspirin/ Acetyl salicylic acid:
  • White crystalline powder for headache and pyrexia
  • S/S- n/v, subconjunctival hemorrhage; petechiae over face and eyelids; gum bleeding, GIT and urethral bleeding; tinnitus and deafness; deep and rapid respiration; pulse rate increased; delirium, agitation, confusion, coma and convulsion; death due to respiratory failure
  • T/t- gastric lavage; KCl to treat hypokalaemia; milk as demulcent; Vit. K for bleeding; oxygen for cyanosis; hemodialysis in very severe cases
  • PM findings- petechial hemorrhage on face and neck; frothy fluid from mouth and nose; cyanosed; erosion of GIT

Heavy metal poisoning:

  • The literature of nineteenth-century European forensic medicine is full of notorious cases of murder by arsenic, antimony and mercury.
  • Arsenic
  • Metallic arsenic,black is not toxic
  • It is the compounds of arsenic, particularly arsenious oxide and the various arsenites of copper, sodium and potassium, that are toxic to humans, inteferes with cellular respiration.
  • Vascular endothelium appears to be particularly susceptible to the toxic effects of arsenic.
  • In acute poisoning, if sufficient chemical is ingested, there may be initial burning in the mouth and then, after an interval, signs of intense gastroenteritis develop: abdominal pain, nausea, burning regurgitation and vomiting. Diarrhoea ensues and this, together with the sickness, leads to prostration, mainly from dehydration and electrolyte imbalance. death in 1 to 3 hrs in severe ac. Poisoning due to shock and peripheral vascular failure.
  • In chronic poisoning, a classic state of ill-health develops, Loss of appetite, mild nausea, some vomiting, jaundice, loss of weight and anaemia are relatively non-specific symptoms.

  • More specific signs can be seen in the skin, where chronic arsenical poisoning causes hyperkeratosis of the palms of the hands and soles of the feet produce band of opacity in the nail k/a MEES-ALDRICH line.
  • A speckled pigmentation of the general skin surface sometimes described as a ‘raindrop’ appearance (finely mottled brown change especially over eyelid,temples,and neck).
  • loss of hair, brittle nails and a peripheral neuritis with itching, tingling and paraesthesia of the extremities
  • The fatal dose is variable, but 200–300 mg of arsenious oxide are likely to be needed for acute fatal toxicity.
  • At autopsy, little may be found in acute deaths apart from a haemorrhagic gastritis. The stomach mucosa has been likened to red velvet, due to the bleeding
  • Subendocardial bleeding may be seen in the left ventricle, though this is not specific to arsenic and can be seen in any death when there has been a precipitous drop in blood pressure due to ‘shock’.

  • T/T-stomach thoroughly washed with fluid,BAL is given,penicillamine may be used in place of BAL.Demulsant decrease the irritation.glucose –saline helpful to combat shock.

Lead

Lead can be administered by oral,inhalation,through skin,mucous membrane,I.V
Causes spasm of capillaries and arterioles
Toxic effects results from fixation of lead into tissues
S/S-
acute poisoning -sweet,metallic taste,burning in throat,V/N,jaundice,feeble pulse,drowsiness,insomnia,headache,convulsion,numbness.
chronic poisoning- anorexia,metallic taste in mouth,constipation,colic,Burton s line(blue pigmentation on gingival margin),anemia and punctate basophilia,peripheral neuritis(foot drop and wrist drop)arthralgias
Management-EDTA as chelating agent,diazepam for convulsion,morphine and pethidine for pain,physiotherapy for paralysis.
MLI-mostly accidental d/t use in utensils,lead pipes.
FD=20-40mg, fatal period =uncertain,2-3 days

Mercury

  • Mercury is usually an industrial or environmental poison.
  • Although historically some deaths occurred from its use in medicine, mercurial diuretics and antiseptics are now almost a thing of the past.
  • Acute poisoning resembles that of arsenic and antimony: gastrointestinal symptoms are common,
  • But there are also excessive salivation and signs of renal failure.
  • Chronic mercury poisoning is almost wholly industrial in nature and
  • The clinical hallmarks are gingivitis, loose teeth, salivation, black gums, mandibular necrosis, peripheral neuritis, encephalopathy and renal failure.