1 forensic science toxicology. 2 why do toxicology? toxicology can: be a cause of death contribute...
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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 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 IDENTIFICATIONScreening 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 TestsChromatography
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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Paper Chromatography
Stationary phase--paper
Mobile phase--a liquid solvent
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
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 Analysisfor Drugs
Blood
Urine
Vitreous
Bile
Liver tissue
Brain tissue
Kidney tissue
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 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.
Symptoms of VariousTypes of Poisoning
Type of Poison Symptom/Evidence• Caustic Poison (lye) 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
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Points to Know about aPoison
Form Common color Characteristic odor Solubility Taste Common sources Lethal dose Mechanism Possible methods of
administration Time interval of onset of
symptoms.
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
ClassPresumptive or screening tests can be used to
determine that it is a drug.
IndividualChromatography, especially in conjunction with
mass spectrometry, will specifically identify a drug or poison and its components.
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
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 InstrumentsThe Breathalyzer – first developed in 1954Collects and measures alcohol content of alveolar breathI 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
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