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What is Forensic Toxicology?
Transcript of What is Forensic Toxicology?
Forensic toxicologists perform analysis of drugs and alcohol in biological samples for the purposes of determining the timing, extent, and impairment resulting from different patters of drug and alcohol use.
The body's natural process generally complicate determining substances because chemicals rarely remain in their original form once they are ingested.
Ex. Heroin is almost immediately metabolized into another substance and then to morphine, making injection marks and chemical purity essential to confirming diagnosis.
Substance may also be diluted throughout the body
An individual sample under investigation might only contain micrograms or nanograms
What is Forensic Toxicology?
is the study of the adverse effects of drugs and chemicals on biological systems.
deals with the application of toxicology to cases and issues where such effects might have legal standing in court. It deals with:
Analysis of drugs in biological materials
Interpretation of those results
Detection and Classification
There are about 21 million registered compounds
Usually done by an initial screening and then a confirmation and quantification of the compound(s).
Choice of testing method is dependent on what kind of substance is suspected and the material on which the testing is performed.
Biological samples are more complex to analyze because of factors such as:
Matrix effect: When other components of a sample interfere with the analysis of the desired component
Conjugation of target compounds
A Forensic Toxicologist's Responsibilities
Collaborate with law enforcement officers, forensic pathologists, other forensic scientists and crime scene investigators
Must consider the context of an investigation.
Symptoms recorded, evidence collected at a crime scene (pill bottles, trace residue, available chemicals, powder)
Must determine which toxic substances are present, in what concentrations and probable effect of substances on victim
Also provide drug testing services for various purposes such as verifying job qualification or if an athlete has used steroids
A urine sample is urine that has come from the bladder and can be provided or taken postmortem.
Many drugs with a higher concentration can remain for much longer in urine than in blood
Solely used for qualitative analysis as it cannot give any indication of impairment due to the fact that drug presence in urine only indicates prior exposure.
A 10 ml blood sample is usually sufficient to screen and confirm most common toxic substances.
Provides a profile of the substance that the subject was influenced by at the time of collection
Sample of choice for measuring blood alcohol content in drunk driving cases
Capable of recording medium to long-term or high dosage substance abuse
Chemicals in the bloodstream may be transferred to growing hair and stored in the follicle, providing a rough timeline of drug intake events.
Head hair grows at about 1 to 1.5 cm a month, so different sections can give estimates as to when a substance was ingested.
The darker and coarser the hair, the more drug will be found in the hair
Raises issues of possible racial bias in substance tests with hair samples
Other bodily fluids and organs may provide samples such as those collected during an autopsy.
Gastric contents which can be useful for detecting undigested pills or liquids that were ingested prior to death (might be unavailable in decomposed bodies)
Vitreous humour from the eye
Brain, liver, and spleen
Additionally bacteria, maggots and other organisms on the body that may have ingested any toxic substance on/in it.
A living person may be tested with a basic kit, such as a breathalyzer for detecting alcohol.
Gas-liquid chromatography is useful in examining volatile organic compounds (vaporize easily)
Process: A sample is vaporized and injected onto the head of a chromatographic column. Chromatography separates the molecules in a mixture. The heavier molecules in the substance will be farther down on the chromatographic column. When the process is complete, there will be stripes of color or substance on the chromatographic column.
Detection of Metals
Compounds suspected of containing metal are traditionally analyzed by the destruction of the organic matrix through chemical or thermal oxidation
Leaves the metal to be identified and quantified in the inorganic residue. Can be detected using:
Reinsch test: Used to identify presence of arsenic, antimony and mercury
Emission spectroscopy: Measurement of radiation intensity as a function of wavelength
X-ray diffraction: Determines atomic and molecular structure
Inconvenient because it removes the original compound
Toxic effects of metallic compounds vary considerably
Nonvolatile Organic Substances
Includes: both prescribed and illicit drugs, pesticides, natural products, pollutants and industrial compounds
immunoassay: measures the presence/concentration of a macro molecule (poison) through the use of an antibody or immunoglobulin
The Importance of Toxicology
For centuries, poisoning has been a popular method of murder
Essential for determining accidental deaths and suicides or substance ingestion/exposure for living people
Disciplines of Forensic Toxicology:
Human Performance Toxicology
Forensic Workplace Drug Testing
Substances in Deaths
Accidental: Can result from overdoses of drugs such as opium,hyoscine,morphine and heroin
Suicide:Carbon monoxide from a car engine, drug overdoses or mixed doses of domestic medications
Murder:Aconitine, atrophine, strychnine, thallium, antimony, arsenic and cyanide
Different effects in different degrees of ingestion
Absorbed from the bowel into the bloodstream then goes into the organs
The liver suffers from the majority of the effects, but in large doses it hits the brain and causes damage there and in the spinal cord
In smaller doses over time, the poison affects the peripheral nerves
Person will feel prickly hear, blisters, severe headaches, nausea, numbness, weakness
A Bungled Test...
The prosecution in France in 1840 of Marie LaFarge, 24, for the murder of her hursband, Charles LaFarge, brought the "science of poisons" into public view.
Marie was accused of using arsenic as a murder weapon
Evidence against her:
Unhappy with arranged marriage (motive)
Purchased large amounts of arsenic preceding Charles' death claiming to exterminate rats
Servants testimony that she stirred white powder into his food
A pharmacist found the food positive for arsenic using the "Marsh" test. However, the prosecution experts could not determine that the contents of Charles' stomach contained arsenic
The "Marsh" test was create by James Marsh and involves treating suspected poisoned material with sulphuric acid and zinc in a closed bottle. From this bottle,emerged a u-shaped glass tupe with one end tapered, through which arsine gas emerged to hit zinc and escape. Said gas could be ignited and then it formed a black mirror substance which indicates arsenic.
Mathieu Orfila, now known as the "father of toxicology", executed the marsh tests again and was able to detect the presence of arsenic in Charles' body.
The previous scientists had bungled the test!
Based on Orfila's results, Marie was convicted.
Ramsland, Katherine. "Forensic Toxicology."
CrimeLibrary: Criminal Minds & Methods. Turner Entertainment Networks, Inc., n.d. Web. 13 Dec. 2013. <http://www.trutv.com/library/crime/criminal_mind/forensics/toxicology/index.html>
"Forensic Toxicology." Forensic Medicine. N.p.,
n.d. Web. 14 Dec. 2013. <http://www.forensic-medecine.info/forensic-toxicology.html>.
"Briefing: What Is Forensic Toxicology."
American Board of Forensic Toxicology. Forensic Toxicology Council, July 2010. Web. 12 Dec. 2013. <http://www.abft.org/files/WHAT%20IS%20FORENSIC%20TOXICOLOGY.pdf>.
"Carbon Monoxide Poisoning - Frequently Asked
Questions." Centers for Disease Control and Prevention. Centers for Disease Control and Prevention, 23 July 2013. Web. 14 Dec. 2013. <http://www.cdc.gov/co/faqs.htm>.
Ellingwood, Ken. "Case Illustrates Rarity of Murder by
Poisoning : Crime: Orange County Death Confounded Investigators for Months. The Victim's Husband Has Been Convicted of Killing Her with Cyanide." Los Angeles Times. Los Angeles Times, 15 May 1995. Web. 15 Dec. 2013. <http://articles.latimes.com/1995-05-15/news/mn-893_1_orange-county>.
Almost any natural substance in the right does can be poisonous
Many poisons mimic common medical diseases, leading physicians to believe a victim died of natural causes
Toxicity of a substance depends on the amount ingested,age, weight, health
Can be administered by ingestion, injection, or absorbed through skin
Method of administration can impact the fatality of a substance
ex. snake venom is only dangerous if it is absorbed in the bloodstream
Colorless, odorless gas
Found in combustion fumes
Symptoms: headache, dizziness, weakness, nausea, vomiting, chest pain, confusion, death
People can die before experiencing the symptoms
If there is a lot of CO in the air, body may replace Oxygen in blood with CO, blocking Oxygen from getting into the body which damages tissues and may result in death.
Yearly American victims:
20,000 emergency room visits
Victim of CO poisoning
Closer to home...
In 1988, Richard K. Overton in Orange County, used one of the rarest murder weapons used in modern America: cyanide.
Only 0.03% of homicides in 1993 were due to poisoning (FBI)
Overton, 66, was convicted for giving a fatal dose of cyanide to his 46-year-old wife, Janet
Initially, however, it wasn't classified as a murder.
Ex-wife of Overton called authorities alleging that he had poisoned her
Authorities proceeded to test Janet's remaining tissue from the autopsy and found cyanide.
Some parting fun facts....
Poison was once dubbed "the coward's weapon"
Bodies are seldom checked for toxic substances unless something points to poisoning
Mithridatium is known as the first "univeral antidote" and is said to cure all types of poisoning
Giulia Tofana (right) was a 17th century Italian woman who murdered about 600 people by selling 'acqua Tofana', a deadly poison containing arsenic which she sold to various people. She made a huge profit because there were so many women wanting to kill their husbands.
Physical manifestation of arsenic poisoning
By Sonia Case