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FORENSIC SCIENCEToxicology

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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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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

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.

Alcohol in theCirculatory System

Forensic ScienceToxicology 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

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

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