Poisoning accounts for less than 10% of homicides – many go undetected due to the difficulty Involves passionate and vengeful murder – requires planning and premeditation
Chapter 8 – Toxicology
Toxicologythe study of the adverse effects of chemicals or physical agents on living organismsMathieu Orfila –father of toxicology
Forensic ToxicologyPostmortem—medical examiner or coronerCriminal—motor vehicle accidentsWorkplace—drug testingSports—human and animalEnvironment—industrial, air, water, soil catastrophic, terrorismConsumer – foods, cosmetics, over the counter drugs
Why we need forensics toxicologistsDeath unattended by a physician or occurring underviolent, unusual or sudden unexplained conditionshappens in approximately 20% of the population andrequires a medical/legal investigation
Forensic Toxicologist☠ Determines if the toxin ☠ Caused the death – a lethal dose ☠ Contributed to death ☠ Caused impairment ☠ Explains behavior
If poison is suspected first step would be to take ablood sampleHomicide poisoning mimics medical situations, a heartattack or diabetic coma. This makes determining thecause of death difficult.
Things to considerDosageChemical or physical form of the substanceMode of entry into the bodyBody weight and physiological conditions of the victim, including age and sexTime period of exposurePresence of other chemicals in the body or in the dose
Toxicology TermsTime of exposure Chronic exposure – long period of time Acute toxicity – immediate effectsOther chemicals/drugs in body Synergism – combination exceeds individual effects Antagonism – combination decreases individual effectsChelating agent – cancels out the poison - antidote
To Prove a CaseProve a crime was committedMotiveIntentAccess to poisonAccess to victimDeath was homicidalDeath was caused by poison
Forensic AutopsyLook for: Irritated tissues Characteristic odors Mees lines—single transverse white bands on nailsOrder toxicological screens Postmortem concentrations should be done at the scene for comparison. No realistic calculation of dose can be made from a single measurement.
Used for AnalysisBlood Liver tissueUrine Brain tissueVitreous humor of eyes Kidney tissueBile Hair/nailsGastric contents
Types of Poisoning Arsenic Cyanide Carbon Monoxide Ricin Lead Poisoning Mercury Poisoning
ArsenicClaimed most victimsNo odor, no tasteFount in insecticides, pesticides and paintsInhaled or swallowed – more than 90% absorbed intoblood
CyanideRapid acting – kills in minutesUsed in photo processingColorless gasStops cellular respiration and ATP synthesis Cells cant use oxygen
Carbon MonoxideColorless, odorless, tastelessFaulty heating systems, car exhaust, firesAbsorbed through lungs
RicinTwice as deadly as cobra venom, two-tenths of amilligram is a lethal dose.ProteinInhaled, injected, ingestedPotential terrorist – Al QuedaDeath 36 – 72 hrs
Lead PoisoningLead compounds not highly poisonous, but chronicexposure can lead to health problemsLead based paints – banned in ’78Tastes sweetStill 38 million houses with lead paint
Mercury Poisoning odorless, colorless, and tasteless Disturbances in sensations ("pins and needles" feelings, numbness) usually in the hands feet and sometimes around the mouth Lack of coordination of movements Impairment of speech, hearing, walking Muscle weakness, skin rashes, mood swingAmalgam dental fillingsconsume mercury-contaminated fishexposed to spilled mercury
AlcoholAlcohol appears in blood within minutes of consumption; 30–90 minutes for full absorptionAbout 5 percent is excreted unchanged in breath, perspiration, and urineRate of absorption Signs of Alcohol Poisoning Amount of alcohol consumed Cold, clammy, pale, or bluish skin The alcohol content of the beverage Unconscious Time taken to consume it Slow or irregular breathing Puking repeatedly or uncontrollably Quantity and type of food present in the stomach Physiology of the consumer
BAC – Blood Alcohol ContentExpressed as percent weight per volume of bloodLegal limit in all states is 0.08 percentBurn-off rate of 0.015 percent per hour, but can vary
Henry’s LawWhen a volatile chemical is dissolved in a liquid and is brought to equilibrium with air, there is a fixed ratio between the concentration of the volatile compound in the air and its concentration in the liquid; this ratio is constant for a given temperature.THEREFORE, the concentration of alcohol in breath is proportional to that in the blood.1 ml of blood will contain nearly the same amount of alcohol as 2,100 ml of breath.
BreathalyzerCollects and measures alcohol content of breathBreath sample mixes with 3 ml of 0.025 percent K2Cr2O7 in sulfuric acid and water: 2K2Cr2O7 +3C2H5OH + 8H2SO4 → 2Cr2(SO4)3 + 2K2SO4 + 3CH3COOH + 11H2OPotassium dichromate is yellow; as concentration decreases, its light absorption diminishes, so the breathalyzer indirectly measures alcohol concentration by measuring light absorption of potassium dichromate before and after the reaction with alcohol.