forensic toxicology

Question 1

the definition of forensic toxicology

Answer 1

the identification and quantification of legal and illegal substances to answer questions to violations of criminal law and manner of death from samples of body fluids, tissues, and organs

Question 2

what are the ante-mortem applications (before death)

Answer 2

blood alcohol level, workplace drug testing, sports-performance enhancing drugs

Question 3

what are the post-mortem applications

Answer 3

poisoning, overdose (accidental/intentional), drug or alcohol contributors to vehicle crashes, workplace injury, or other fatal incidents

Question 4

examples of body fluids’ samples for toxicology

Answer 4

blood, urine, vitreous humor, hair, breastmilk, feces, meconium

Question 5

alcohol absorption in the beginning

Answer 5

blood concentration of alcohol slowly rises through absorption from the stomach where ~20% of the alcohol is absorbed and the small intestine where the rest is absorbed

Question 6

alcohol absorption in the end

Answer 6

reaches lungs, allowing for the exchange of alcohol from the blood to the lungs to be transported by the trachea

Question 7

describe alcohol metabolism

Answer 7

individuals w/ low ALDH (acetaldehyde dehydrogenase) levels or ALDH2 accumulate acetaldehyde , which has a powerful vasodilation effect, leading to unpleasant side effects including flushing and hangover-like symptoms

Question 8

ADH (alcohol dehydrogenase)

Answer 8

enzymes that convert ethanol to acetaldehyde (more toxic than ethanol)

Question 9

ALDH (acetaldehyde dehydrogenase)

Answer 9

enzymes that metabolize the acetaldehyde to yield acetic acid (non-toxic)
1. ALDH1 (cytosol)
2. ALDH2 (mitochondria — high activity)

Question 10

describe alcohol excretion

Answer 10

alcohol and its detoxification products are excreted through the skin, breathe and urine
1. CO2 is transported and excreted through the breath
2. some alcohol is also excreted as volatile oxygen vapors
3. a small amount is excreted through the skin due to perspiration

Question 11

what are alcohol deterrent drugs

Answer 11

used to treat alcoholism
1. antabuse
2. naltrexone

Question 12

the absorption rate of blood alcohol concentration (BAC) is affected by:

Answer 12

1. time it takes to consume the alcoholic drink(s)
2. alcohol content (proof)
3. amount of alcohol consumed
4. body weight
5. tolerance of the individual
6. sex of the individual
7. presence or absence of food in the stomach

Question 13

BAC computation equation

Answer 13

Cp = D / ((Vd)(W)) * 100 = %

Cp (blood conc.) = D (dose) / (Vd distribution volume)(W weight in grams)

Question 14

percentage range for noticeable cognitive changes from alcohol consumption present in blood alcohol

Answer 14

0.02-0.03%

Question 15

in the us, the legal limit of alcohol in the blood (%) is

Answer 15

0.08% for the person operating a motor vehicle

Question 16

describe GC-MS BAC testing

Answer 16

the quantity of alcohol is determined using the area under the alcohol peak recorded on the GC chromatogram by comparing the peak area of the unknown to the peak areas of alcohol standards of known concentrations

Question 17

henry’s law equation

Answer 17

when a volatile chemical is dissolved (blood) and brought to equilibrium with air in the alveoli, the pressure of the gas divided by the concentration of the mass in the liquid is constant
k = pgas / caq

Question 18

breathalyzer

Answer 18

• alcohol (ethanol) is reacted with the potassium dichromate reagent under acidic conditions and using a silver nitrate catalyst, the chromium sulfate product is detected using spectrometry at a fixed wavelength
• the instrument uses the absorbance intensity to calculate the blood alcohol concentration

Question 19

fuel cell test

Answer 19

• the fuel cell breath test determines the quantity of alcohol in the blood using the alcohol as a fuel that is ignited and burned in the presence of oxygen creating energy that is converted to an electrical current
• the change in resistance is measured by a detector

Question 20

intoxilyzer IR roadside breath test

Answer 20

the quantity of alcohol in the blood is evaluated indirectly using the breath. It determines the decrease in light transmitted in the presence of the alcohol compared to the light transmitted in the alcohol-free control sample

Question 21

evidence considerations regarding to illegal drugs

Answer 21

1. pills
2. powders
3. empty pill containers
4. drug paraphernalia (materials used for the drug ; e.g. bongs/needles)
5. photos of foaming or blood from nose/mouth (overdose indication)
6. notes/text messages (was it suicidal? who was the dealer?)

Question 22

the analytical scheme of drug screening

Answer 22

to detect, isolate, and specifically identify poisons and drug substances
based upon chemical properties of the substances being tested including acidity (e.g., barbiturates, aspirin) and basicity (e.g., phencyclidine, methadone, amphetamines, crack cocaine)

— first screening then confirmatory methods —
1. screening: color tests, immunoassays, microscopy, chromatography
2. samples may need to be separated from the body fluid or may be analyzed in situ
3. confirmatory tests include MS, FT-IR, NMR

Question 23

what you can detect drugs depends on

Answer 23

1. body fluid
2. dose
3. drug type
4. individual metabolism
5. body hydration
6. condition of body post-mortem

Question 24

methods to identify gaseous poisons

Answer 24

1. UV-vis spectroscopy: detect O2Hb vs COHb (Hb binds CO 200 times more strongly than O2)
2. GC-MS

Question 25

method to identify heavy metal poisons

Answer 25

reisch color test: piece of tissue homogenate or body fluid is placed in hydrochloric acid and a copper strip is placed in the sample, a silvery or dark coating on the copper indicates the presence of a heavy metal

Question 26

other identification methods for poisons

Answer 26

1. atomic absorption spectroscopy 2. x-ray fluorescence spectroscopy 3. emission spectroscopy – bands, color of metal 4. x-ray crystallography – structure of compound