Toxicology & Poisons

Poisons and Toxins Two general categories: 1. Corrosive Poison ex. acids or bases 2. Metabolic poisons: act on biochemical process ex. carbon monoxide, cyanide, heavy metals (lead, mercury, arsenic)

Poisons ANY substance that when taken in sufficient quantities causes a harmful or deadly reaction. (Sufficient quantities – how much enters the body, over what period of time) 1. Intoxicant requires an ingestion of large quantities before it is lethal Ex: Carbon Monoxide, Alcohol, heavy metals (mercury, lead, selenium) 2. “True” Poison – requires only a tiny amount Ex: Cyanide

Effects of Toxins Effects of toxins do not cause VISIBLE changes in the body in living people or during an autopsy. Medical Examiner will collect fluids and tissues for testing Toxins are sneaky! Biotransformation can change one chemical into another within the body due to metabolism. The toxicologist may have to look for a different sign of the toxin.

Sample Testing Blood – most useful… tells what is going on at the time of death. Urine – Easily obtained… can’t determine whether a drug was exerting any effect at time it was collected. Stomach Contents Liver Vitreous Humor – eyeball fluid… resists decay…may be the only fluid left in a decaying body Hair – absorbs heavy metals and provides timeline of ingestion Insects – that feed on the corpse will have elevated levels of certain drugs

Points of Administration Toxins will be most concentrated at the point of entry: a. Ingested Toxins – show up more in the stomach, intestines, and liver b. Inhaled Toxins – show up in the lungs c. Injected Toxins – linger in tissues around point of injection; muscle slows down the transfer to the bloodstream. d. Intravenously (IV) – will bypass the stomach and liver going directly into the bloodstream therefore quickly distributed

Familiar Poisons Cyanide – very lethal ME will notice a BRIGHT cherry red color to the victim’s blood. Strychnine – plant based rat poison Extremely bitter taste: hard to disguise Causes a LOT of pain: Not typical in suicides Causes convulsions Death is caused by asphyxia

Poisons Continued… Ethylene Glycol – antifreeze ME will find crystals in tubules of kidney Heavy Metals – Arsenic, Mercury, Lead, Thallium All behave slightly different but cause gastrointestinal injury Leads to nausea, vomiting, diarrhea (bloody) Damages kidneys, liver, brain, and nerves Arsenic poisoning often is mistaken for food poisoning Mercury poisoning causes brain damage and birth defects

More Poisons… Succinyl Choline – injectable drug paralyzes all the muscles of the body Leaves behind little evidence of presence Corrosive Chemicals – Strong alkalis bases (lye) and acids When ingested…corrode and burn tissues of digestive track Causes bleeding, shock, and death Rarely used in homicides…mostly accidental children ingestion. Carbon Monoxide – metabolic poison Prevents oxygen from binding to hemoglobin in red blood cells “Silent Killer” – causes suffocation

ALCOHOL Blood Alcohol concentration BAC is the amount of alcohol in the bloodstream measured in percentages BAC = 0.10% means a person has 1 part alcohol per 1,000 parts of blood in the body The ratio of alcohol in blood to alcohol in alveoli air is 2100 to 1 (1 mL of blood will contain about the same amount of alcohol as 2100 mL of breath)

Alcohol Effects % w/v is g per 100 mL Mild Intoxication (BAC = 0.050 %w/v) - Feeling of warmth, skin flushed, impaired judgment, decreased inhibitions. Obvious Intoxication in most people (BAC = 0.100 %w/v) - Increased impaired judgment, inhibition, attention, slowed reflexes. Obvious Intoxication in all "normal" people (BAC = 0.150 %w/v) - General lack of muscle coordination, slurred speech, double vision, memory and comprehension loss. Extreme intoxication (BAC = 0.250 %w/v) - Reduced responsiveness, inability to stand, vomiting, incontinence, sleepiness. Coma occurs around 0.350 %w/v and death is likely at 0.500 %w/v.   % w/v is g per 100 mL

BAC FIELD SOBRIETY TESTING Portable, roadside breath tester. Breath Testing - direct relationship between BAC and amount of alcohol vapor in breath. Walk and turn and/or one leg stand (divided attention test). Horizontal gaze nystagmus- involuntary jerking of eye as it moves to the side - more intoxicated the less the eye moves before jerking.

Legal Aspects Schmerber v. California (1966) Pled 5th Amendment (not to self-incriminate). Supreme court ruled against him, stating the 5th Amendment protects testimonial evidence not physical evidence - therefore, he had to give his blood for testing. Also ruled against Schmerber on Search and seizure stating that blood sampling is an “emergency” procedure since by the time a search warrant was obtained the BAC would have dropped (destruction of evidence) Sample must be taken in a medically acceptable way without unreasonable force and related to an accident or arrest. Federal Law - driving on road gives “implied consent” for testing (either take test or lose license).