Toxicology

1. Forensic Toxicology

2. Toxicologists
Detect and identify the presence of drugs
and poisons in body fluids, tissues, and
organs
Work in health facilities such as hospitals
and clinics as well as crime labs
Most frequently asked to determine the
presence of alcohol in the body

3. Alcohol is the most
widely abused drug in
western countries.
Due to prevalence of
abuse, laws have
been instituted to
regulate driving while
under the influence –
intoxication.

4. The degree of intoxication can be
influenced by:
Body weight
Rate of absorption through stomach and small
intestines directly into the blood stream
Influenced by presence/absence of food
Total time taken to consume the alcohol
Type of alcohol consumed – diluted/undiluted
The longer total time required for complete
absorption, the lower will be the peak alcohol
concentration

5. Methods had to be
developed to assess
levels of intoxication
at the time of arrest
These had to be
reliable to withstand
court presentation

6. What does Alcohol do to the Body?
It depresses the CNS – Brain
Extent of depression is directly proportional to
concentration of alcohol within the nerve cells
Specifically the forebrain
Eventually alcohol will affect the central and
rear portions of the brain
Most resistant and last to fail are in the
medulla which regulates respiration and heart
activity

7. Most tests rely on blood – the medium for
circulating alcohol throughout the body
Research confirms the direct proportional
relationship of:
Blood alcohol concentration to brain alcohol
concentration
Maximum Blood Alcohol Content (BAC) may
not be reached until 2-3 hours after time of
consumption – more likely within 30-90 min.
from final drink until absorption process is
complete
What does Alcohol do to the Body?

8. Alcohol will become uniformly distributed
throughout the watery portion of the body
at complete absorption – 2/3 of body
volume
Liver begins the elimination process of 95-
98% of the alcohol by oxidation
In the presence of the enzyme alcohol
dehydrogenase, alcohol is converted into
acetaldehyde and then to acetic acid which is
oxidized to carbon dioxide and water
What does Alcohol do to the Body?

9. Remaining 2-5% is excreted unchanged in
the breath, urine, and perspiration.
Amount exhaled is in direct proportion to
concentration of alcohol in the blood
Using Henry’s Law, Alveoli air is approximately
2,100:1 – alcohol content in 1 ml of blood =
2,100 ml of alcohol content in alveoli air
Elimination or “burn off” rate can vary by
30% between individuals, but average is
0.015% w/v (weight/vol.) per hour
What does Alcohol do to the Body?

10. Alcohol’s movement through the circulatory
system
After alcohol is ingested it moves down the
esophagus into the stomach – where about 20% of
the alcohol is absorbed through the stomach lining
into the portal vein.
Remaining 80% is absorbed into the blood through
the lining of the small intestines
Once in the blood it is transported to the liver, heart,
lungs, back to heart to be distributed to all parts of
the body
What does Alcohol do to the Body?

11. 1. Blood rich in carbon dioxide is pumped
from the heart into the lungs through the
pulmonary arteries. (Arteries are blood
vessels carrying blood away from the heart;
veins are blood vessels carrying blood to the
heart.)
2. In the lungs, CO2 in the blood is
exchanged for O2.
3. The oxygen-rich blood is carried back to
the heart through the pulmonary veins.
4. This oxygen-rich blood is then pumped
from the heart to the many tissues and
organs of the body, through the systemic
arteries.
5. In the tissues, the arteries narrow to tiny
capillaries. Here, O2 in the blood is
exchanged for CO2.
6. The capillaries widen into the systemic
veins, which carry the carbon-dioxide-rich
blood back to the heart.
Circulatory/Respiratory System

12. Circulatory/Respiratory System

14. During period of alcohol absorption,
alcohol concentration within arterial
(oxygenated) blood will be considerably
higher than in venous (deoxygenated)
blood.
Blood drawn for testing comes from the
veins in the arm. The true level of alcohol
may not be accurate during the early
phases of absorption. Alcohol levels will
equalize as absorption continues into later
and final stages.

15. Breath-Test Instruments

16. Breathalyzer Test
Widely used until
1990
A device for collecting
and measuring the
alcohol content of
alveolar breath

17. A subject blows into a mouthpiece that
leads to a metal cylinder which causes a
piston to rise to a height that exposes two
vent holes. When collection of alveolar
breath is complete the piston drops back
into place trapping the collected ~52.5 ml
or 1/40 of 2.100 ml of alveolar breath.
Breathalyzer Test

18. This trapped alveolar breath can then be
analyzed as it passes into a glass ampoule
containing 3 ml of 0.025% potassium
dichromate and 0.025% silver nitrate in
sulfuric acid and water.
Any alcohol present in the sample
dissolves in the dichromate solution and is
oxidized to acetic acid.
Breathalyzer Test

19. The oxidation process destroys the potassium
dichromate – the extent of which is measured by
the Breathalyzer and relates to the quantity of
alcohol passed into the ampoule.
This is a spectrophotometer specially designed
to measure the absorption of light passing
through the potassium dichromate solution at a
single wavelength.
Breathalyzer Test

20. REACTION:
2K2Cr2O7 + 3C2H5OH + 8H3SO4
Potassium Ethyl Sulfuric
dichromate alcohol acid
2Cr2(SO4)3 + 2K2SO4 + 3CH3COOH + 11H2O
Chromium Potassium Acetic Water
sulfate sulfate Acid
Breathalyzer Test

21. Potassium dichromate
Yellow in color and absorbs visible light
wavelengths of 420 nm
The Breathalyzer indirectly determines the
quantity of alcohol consumed by
measuring the absorption of light by
potassium dichromate before and after its
reaction to alcohol
Breathalyzer Test

22. Newer Technology - Infrared
Designed to minimize operator
error and free of chemical
reagents
Operates on infrared light
absorption and/or fuel cells
Infrared light absorption uses
filters selected to a wavelength of
infrared light at which alcohol will
absorb.
Greater alcohol concentration
decreases intensity of light measured
by a photoelectric detector

23. Infrared light signal is proportional to
concentration of alcohol present in captured
breath sample
Processed by an electronic microprocessor and
% BAC is displayed in a digital readout on a card
for permanent record
A second simultaneous infrared wavelength is
also used to check for acetone or other chemical
interferences and warns operator of the
presence of an “interferant”
Newer Technology - Infrared

24. Fuel cell converts a fuel and an oxidant
into an electrical current.
Breath alcohol = the fuel
Atmospheric oxygen (O2) = oxidant
Alcohol is converted into acidic acid within the
fuel cell which generates a current that is
proportional to the quantity of alcohol present
in the breath.
Device is microprocessor controlled which reduces
operator error and provides a printout for
permanent record
Newer Technology – Fuel Cell

25. Newer Technology – Fuel Cell

26. Newer Technology
Both techniques utilize a slope detector
which insures that the sample
administered is from deep long breaths
which relate to the true BAC of the subject
being tested

27. Field Sobriety Tests
Normally performed to ascertain the
degree of the suspect’s physical
impairment and whether or not an
evidential test is justified.
Roadside breath tests
Preliminary and non-evidential
Probable cause for later tests

28. Psychophysical tests – reliable and effective
Horizontal gaze nystagmus,
Involuntary jerking of eye as it moves to side as
intoxication increases the ability of the eye to follow an
object as it moves to the side without jerking decreases.
If BAC is at .10%, eye jerking will begin at 45° angle as
BAC increases jerking will begin at increasingly small
angles
Walk and turn – a divided attention task
Tests subject’s ability to comprehend and simultaneously
carry out more than two instructions. This ability
decreases with increasing consumption of alcohol
One leg stand – a divided attention task
Field Sobriety Tests

30. Analysis of Blood for Alcohol
Gas Chromatography
Alcohol is separated from other volatiles in blood.
Compares resultant alcohol peak area to ones
obtained with known blood-alcohol standards
Can be calculated with a high degree of accuracy
Oxidation of alcohol to acetaldehyde in the presence
of the enzyme alcohol dehydrogenase ad a coenzyme
nicotin-amide-adenine dinucleotide (NAD). As
oxidation proceeds, NAD NADH. The extent of
conversion is related to alcohol concentration.

31. Collection and Preservation of
Blood – Live Suspect
Must be drawn under medically accepted
conditions by a qualified person
Must use a sterile needle or lancet
Cleanse with a non-alcoholic disinfectant
such as:
Aqueous benzalkonium chloride (Zepiran)
Aqueous mercurie chloride
Providone-iodine (Betadine)

32. Seal blood sample in an airtight container
with an anticoagulant (EDTA or Potassium
oxalate) and preservative (sodium
fluoride)
Place in refrigerated storage for delivery to
toxicology ASAP
If procedures are not strictly adhered to,
then BAC decreases and never increases –
so sloppy police and lab work benefits the
suspect.
Collection and Preservation of
Blood – Live Suspect

33. Requires added precautions
Must account for bacterial action so collect
from a number of different body sites.
Each sample is kept in separate airtight containers
with an anticoagulant, sodium fluoride, and
refrigerated.
Collect urine and vitreous humor fluids – both
usually do not suffer from postmortem ethyl
alcohol production to any significant extent.
Collection and Preservation of
Blood – Postmortem Samples

34. Alcohol and the Law
A BAC of .08% or
.10% in most states
in equivalent to
intoxication for most
drivers
Federal standard for
bus and truck
operators is .04%

35. Implied consent comes with obtaining a license
to operate a motor vehicle
Driver has a choice – submit to test or be
subject to loss of license for a given period of
time.
Schmerber v. California
Court ruled against defendant – the Fifth Amendment
only prohibits self-incrimination. Being compelled to
furnish “physical” evidence such as fingerprints,
photographs, measurements, and blood samples are
not protected by the Fifth Amendment
Alcohol and the Law

36. Role of the Toxicologist
First attempt to narrow down type of toxic substance
based on victim’s symptoms, postmortem pathological
exam, exam of victim’s personal effects, nearby
presence of empty drug containers or household
chemicals
Next, use general screening procedures
Test for small quantities that may be remaining
Must be aware that the body always processes
substances – few substances enter and completely leave
the body in the same chemical state – most are
metabolized – so test for the metabolite
Must also assess for substance’s toxicity

37. Toxicological Techniques
90% of drugs analyzed is for alcohol and
cocaine
The toxicologist must devise an analytical
scheme that will successfully detect, isolate, and
specifically identify a toxin
Large number of drugs are either acidic (H+) or
alkaline (OH-)
By controlling the pH of a water solution into which
blood, urine, or tissues are dissolved, the toxicologist
can control the type of drug that will be recovered.

38. Acidic Drugs
Acid drugs are extracted from an acidified
water solution with organic solvents such
as chloroform.
Barbiturates
Acetylsalicylic acid (aspirin)

39. Alkaline (Basic) - Drugs
Basic drugs are extracted from an alkaline
water solution with organic solvents
Phencyclidine
Methadone
Amphetamines
Cocaine

40. Sample
Acidic Drugs Basic Drugs
Extraction at appropriate pH
SCREENING TEST
Immunoassay
Gas Chromatography
Thin-Layer Chromatography
CONFIRMATION TEST
Gas Chromatography-Mass Spectrometry

41. Heavy Metal Poisons
Rarely encountered
Arsenic, bismuth, antimony, mercury, and
thallium
Extraction into HCL solution – insert a copper
strip (Reinsch Test) – positive presence of a
heavy metal will develop a silvery or dark
coating on the copper.
Confirm with atomic absorption
spectrophotometry, emission spectroscopy, or
X-Ray differaction

42. Carbon Monoxide – A Commonly
Encountered Poison
CO binds with hemoglobin carboxyhemoglobin
Methods to determine concentration of CO in the
blood:
Spectrophotometric methods examine bloods visible
spectrum to determine the relative amount of
carboxyhemoglobin to oxyhemoglobin or total
hemoglobin
Treat a volume of blood with a reagent to liberate the
CO then measure with gas chromatography.
Measured as percent saturation – 50-60% saturation
is considered fatal when combined with .2% BAC 35-
45% saturation maybe fatal

43. Smokers usually have an 8-10% saturation
In fire evaluation – determination of victim’s
condition prior to fire.
If victim was alive at time of fire they would
have a high % CO saturation
If victim was dead at time of fire they would
have low % CO saturation since they could not
breath in any of the fumes
Carbon Monoxide – A Commonly
Encountered Poison