Toxicology Forensics Foster

Toxin Substance that can cause injury to the health of a living thing on contact or absorption –Usually reserved for naturally produced substances that kill in small quantities

Factors affecting Toxicity 1.Dosage- amount and frequency 2.The chemical or physical form of the substance 3.The mode of entry into the body 4.Body weight and physiological conditions of the victim, including age and sex 5.The time period of exposure 6.The presence of other chemicals in the body or in the dose

Example Arsenic is a metal –Rather insoluble in stomach acid As 2 O 3 and extremely toxic As 2 O 5 Arsine AsH 3 is a gas that can kill Small amounts of arsenic are good for you and you are exposed to all the time

Factors (cont.) Lethal Dose –LD 50 refers to the dose of a substance that kills 50% of the test population, usually within 4 hours Expressed in mg of substance per kg of body weight Chemical or physical form of the substance –Solid, liquid … How it enters the body –Blood, absorption… Body weight and physiological conditions of the victim, including age and sex –Larger doses are required for a big person

Time period of exposure –Chronic exposure- exposure over a long period of time –Acute toxicity- effects almost immediately (hrs. or days) Factors (cont.) Violin markings

Factors (cont.) Presence of other chemicals in the body – Synergism- combined effect of substances exceeds sum of individual effect –Antagonism- combined effect decreases individual effects –Chelating agent- stabilize or prevent the precipitation of damaging compounds Red Hourglass

Measuring Toxicity Humans based on animal LD 50 (Rat, oral)Correlation to Ingestion by 150-lb Adult Human Toxicity <1 mg/kga taste to a dropextreme 1–50 mg/kgto a teaspoonhigh 50–500 mg/kgto an ouncemoderate 500–5,000 mg/kgto a pintslight 5–15 g/kgto a quartpractically nontoxic Over 15 g/kgmore than 1 quartrelatively harmless

To Prove a Case Prove a crime was committed Motive Intent Access to poison Access to victim Death was homicidal Death was caused by poison

Alcohol Most abused drug in US ~40 % of accidents related to alcohol Tests –Field One leg stand 9 step walk & turn Nystagmus– –jerky eye –Breath Analysis –Blood Analysis