Transcript FORENSIC SCIENCE

FORENSIC SCIENCE
Toxicology
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Why do Toxicology?
Toxicology can:
• Be a cause of death
• Contribute to death
• Cause impairment
• Explain behavior
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OUR STUDY
 Drugs
 Poisons
Basically, toxicology involves the separation,
detection, identification and measurement of the drug
and/or poison.
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Testing
 PDR’s--Physician’s
Desk Reference
 Field Tests--presumptive tests
 Lab Tests--conclusive tests
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Analysis of Drugs
 Controlled
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Substances Act
Schedule I--heroin, LSD
Schedule II--morphine, methadone
Schedule III--barbiturates, amphetamines
Schedule IV--other stimulates and
depressants
Schedule V--codeine
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DRUG IDENTIFICATION
Screening tests or
presumptive tests
 Color tests
 Microcrystalline test-a reagent is added that
produces a crystalline
precipitate which are
unique for certain
drugs.
Confirmation tests
 Chromatography
 Spectrophotometry
 Mass spectrometry
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Presumptive Color Tests
 Marquis--turns
purple in the presence of
most opium derivatives and orange-brown
with amphetamines
 Dillie-Koppanyi--turns violet-blue in the
presence of barbiturates
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Presumptive Color Tests
 Duquenois-Levine--turns
a purple color in
the presence of marijuana
 Van Urk--turns a blue-purple in the
presence of LSD
 Scott test--color test for cocaine
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Confirmation Tests
Chromatography
 Techniques
for separating mixtures into
their component compounds
 Includes two phases--one mobile and one
stationary that flow past one another
 As the mixture separates it interacts with the
two phases.
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Types of Chromatography
 Paper
 Thin
Layer
 Gas
 Pyrolysis
Gas
 High Pressure Liquid (HPLC)
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Paper Chromatography
Stationary phase-paper
 Mobile phase--a liquid
solvent
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Capillary action moves
the mobile phase
through the stationary
phase
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Thin Layer Chromatography
Stationary phase--a
thin layer of coating
on a sheet of plastic or
glass (usually
aluminum or silica)
 Mobile phase--a liquid
solvent
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from www.lbp.police.uk
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Retention Factor (Rf)
If the Rf value for an unknown compound is
close to or the same as that for the known
compound, the two compounds are most
likely similar or identical (a match)
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GC Analysis
 Shows
a peak that is proportional to the
quantity of the substance present
 Uses retention time instead of Rf for the
quantitative analysis
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Pyrolysis Gas
Chromatography
 Used
when a sample does not readily
dissolve in a solvent
 If heating this sample decomposes it into
gaseous products, these products can be
analyzed by CGC
 A pyrogram is the visual representation of
the results
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Mass Spectrometry
Gas chromatography has one major drawback--it
does not give a specific identification. By teaming
a gas chromatograph with a mass spectrometer,
this is accomplished.
The mixture is separated first in a gas
chromatograph. The GC column is directly
attached to the mass spectrometer where a beam of
electrons is shot through the sample molecules.
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MS (cont.)
The electrons cause the molecules to lose electrons
and become positively charged. These are unstable
and decompose into many smaller fragments.
These fragments pass through an electric or
magnetic field and are separated according to their
masses.
NO TWO SUBSTANCES PRODUCE THE
SAME FRAGMENTATION PATTERN.
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Human Analysis
for Drugs
 Blood
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Liver tissue
 Urine
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Brain tissue
 Vitreous
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Kidney tissue
 Bile
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Spleen tissue
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“If all those buried in our
cemeteries who were poisoned
could raise their hands, we would
probably be shocked by the
numbers.
--John Trestrail
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POISONERS in HISTORY
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Olympias—a famous Greek poisoner
Locusta—personal poisoner of Emperor Nero
Lucretia Borgia—father was Pope Alexander VI
Madame Giulia Toffana—committed over 600 successful
poisonings, including two Popes.
Hieronyma Spara—formed a society to teach women how
to murder their husbands
Madame de Brinvilliers and Catherine Deshayes—French
poisoners.
AND many others through modern times.
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Symptoms of Various
Types of Poisoning
Type of Poison
• Caustic Poison (lye)
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Symptom/Evidence
Characteristic burns around the lips
and mouth of the victim
Carbon Monoxide
Red or pink patches on the chest and
thighs. Unusually brighter red lividity
Sulfuric acid
Black vomit
Hydrochloric acid
Greenish-brown vomit
Nitric acid
Yellow vomit
Phosphorous
Coffee brown vomit. Onion or garlic
odor
Cyanide
Burnt almond odor
Arsenic, Mercury
Pronounced diarrhea
Methyl (wood) or
Nausea and vomiting,
Isopropyl (rubbing) alcohol unconsciousness, possibly blindness
Points to Know about a
Poison
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Form
Common color
Characteristic odor
Solubility
Taste
Common sources
Lethal dose
Mechanism
Possible methods of
administration
Time interval of onset of
symptoms.
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Symptoms resulting from an
acute exposure
Symptoms resulting from
chronic exposure
Disease states mimicked by
poisoning
Notes relating to the victim
Specimens from victim
Analytical detection methods
Known toxic levels
Notes pertinent to analysis of
poison
List of cases in which poison
was used
from “Criminal Poisoning” by John Trestrail
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Evidence
 Class
Presumptive or screening tests can be used to
determine that it is a drug.
 Individual
Chromatography, especially in conjunction with
mass spectrometry, will specifically identify a
drug or poison and its components.
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Alcohol in the
Circulatory System
Forensic Science
Toxicology Unit
How to measure Alcohol ingested
 Two
ways to measure alcohol in the
blood:
1. Direct chemical analysis of blood
2. Measure alcohol content of the
breath
Pathway of Blood
 20%
of alcohol ingested is absorbed
thru stomach walls into the portal
vein
 Remaining alcohol passes into the
small intestine
 Once in the blood the alcohol goes to
the liver and moves up to the heart
 Eventually, blood makes its way to
the lungs
Alveoli
 250
million in lungs, located at the
terminal ends of bronchial tubes
 It is the surface of these alveolar
sacs that blood flowing through the
capillaries comes into contact with
fresh oxygenated air in the sacs
Pathway cont.
 CO2,
alcohol, or any other volatile
substance will move from the
capillaries into the air sacs to be
exhaled
 Oxygen moves into the air sacs
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Henry’s Law
When a volatile liquid (alcohol) is dissolved in a liquid
(blood) and is brought to equilibrium with air (alveolar
breath) there is a fixed ratio between the
concentration of the volatile compound (alcohol) in
the air (alveolar breath) and its concentration in the
liquid (blood) and this reaction is constant for a given
temperature (34°C)
The ratio of alcohol in the blood to alcohol in alveolar
air is approx. 2100 to 1…..in other words 1 mL of blood
will contain nearly the same amount of alcohol as 21
mL of alveolar breath….
Thus….. Henry’s Law becomes a basis for relating
breath to blood alcohol concentration!
Breath Test Instruments
The Breathalyzer – first developed in
1954
Collects and measures alcohol content
of alveolar breath
I t is a spectrophotometer that has
been designed to measure the
absorption of light passing thru the
K2Cr2O7 (potassium dichromate) solution at a
single wavelength
IR absorption and/or with fuel
cell
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Alcohol present is captured in breath chamber
a beam of infrared light is aimed through the
chamber
A filter is used to select a wavelength of IR light
at which alcohol will absorb
Information is processed by a microprocessor and
the percent blood-alcohol concentration is
displayed on a digital readout
It is also printed on a card to produce a permanent
record of the test results
Field Sobriety Testing
 Performed
to ascertain the degree of
the suspect’s physical impairment and
whether or not an evidential test is
justified.
Psychophysical tests
 Horizontal
gaze nystagmus
• Refers to an involuntary jerking of
the eyes as they move to the side
• When bac is 0.10 %the jerking will
begin before the eyeball has moved
45 degrees to the side
 Higher
bac will cause jerking at
smaller angles
 Barbituates/depressants can cause
nystagmus
Walk & Turn;
One-Leg Stand
 Tasks
test the subject’s ability to
comprehend and accomplish two or
more simple instructions at one time