Forensics Unit 3 Notes Chapter 8 – Toxicology: Poison and Alcohol I. History

Forensics Unit 3 Notes
Chapter 8 – Toxicology: Poison and Alcohol
a. Parcelsus- substances that kill at high doses are actually beneficial at low doses
i. The poison is in the dosage
b. Forensic Toxicology- 1814, the study of the adverse effects of chemicals or physical agents on
living organisms
Factors effecting toxicity
a. Dosage- amount of toxin as well as frequency
i. Lethal Dose
1. LD50 refers to the dose of a substance that kills 50% of the test population, usually
within 4 hours
2. Expressed in mg of substance per kg of body weight
b. Chemical or physical form of the substance
i. Solid, liquid …
ii. Isotope- chemical elements that have the same # of protons but different # of neutrons
1. Po210 is an isotope of Polonium that is very dangerous where Po209 isn’t as toxic
2. Po210 has a half-life – (time it takes for ½ sample to decay) of 138 days which is
very short
c. How it enters the body
i. Blood, absorption…
d. Body weight and physiological conditions of the victim, including age and sex
i. Larger doses are required for a big person
e. Time period of exposure
i. Chronic exposure- exposure over a long period of time
ii. Acute toxicity- effects occur almost immediately (hrs. or days)
f. Presence of other chemicals in the body or dose
i. Synergism- combined effect of substances exceeds sum of individual effect
ii. Antagonism- combined effect decreases individual effects
iii. Chelating agent- stabilize or prevent the precipitation of damaging compounds
Toxicology to prove a case
a. Prove a crime was committed
b. Motive
c. Intent
d. Access to poison
e. Access to victim
f. Death was homicidal
g. Death was caused by poison
Alcohol – Ethyl Alcohol (C2H5OH)
a. Most abused drug in the US- depressant
b. DUI- Driving Under the Influence
c. Field sobriety test
i. One leg stand, comprehend and execute 2 or more simple instructions
1. Counting, alphabet forward or backward
ii. Walking a straight line (9 step walk and turn)
iii. Nystagmus- rapid involuntary jerking of the eyeball
1. Move an object side to side ~12in . from persons face
2. intoxicated person can not follow object smoothly
d. Breath testing technology
i. Uses IR spectroscopy