Forensic Toxicology

What type of toxicology is the backbone of Forensic Toxicology

analytical toxicology

Applying chemistry to identify presence and amount of chemicals —> used to predict pass events on a living organism

What is the order of most important chemicals you should be identifying

1. Gases

2. Volatile substances

3. Corrosive agents

4. Metals

5. Anions and non-metals

6. Non-volatile organic substances

7. Miscellaneous

How are chemicals extracted from biological matrices

• Chemicals are isolated by fractionations

• If iterative (if a mix), increases solvent polarity with each extraction (start with low polar and go higher)

What does post-mortem investigations look at

include qualitative/quantitative analysis of chemicals in biological specimens collected at autopsy + interpretations of these findings on behavioural and physiological effects at the time of injury/death

What is the difference between manner and cause of death

• Manner = may have lead to someone death but wasn’t the direct reason

  • May be on a drug and they jump off the building. The drug didn’t kill them the fall did effected the manner in how they died

• Causes = directly causing death

  • Drug causing someone liver to shut down = direct cause of death

What is really important with samples (2)

Chain-of-custody tracks who was in charge of the specimen at all times → allows a court to hear the evidence

Good lab practices (e.g. standards, purity, calibration, record keeping) ensure high quality data

What are the 3 general step of investigating a poisoning death

1) Obtain case history and specimens,

2) Toxicological analyses, and

3) Interpretation of toxicological findings

What does a case history may look like

• Age, sex, weight, medical history, occupation, treatments before death, gross autopsy findings, drugs available to deceased, interval between onset of symptoms and death, possible toxin identification at the death scene

• Pathologist at autopsy collects specimens for toxicological analysis

What does specimen collection look like

• Samples are collected before embalming (preserving) happens as the chemicals used in embalming may dilute poisons or render them indetectable

• Limited amount of sample are collected so have to think about how these sample are going to before hand by predicting what is going on

• Typical sample are blood, urine, liver, stomach contents

• Extended sampels include bone marrow, hair, nails, even insects from putrefying corpses can provide chemicals for analysis of death

What type of chemicals can be found in the

• Vitreous humour of eye good for finding drugs, anions, volatile poisons like alcohols, ketones, glycols'

What type of chemical can be found in the hair

• Hair heavy metals arsenic mercury lead, drugs of abuse, pharmaceuticals, pesticides and plastics

What can a maggot analysis tell you

yield positive screens for barbiturates, benzos, phenothiazines, morphine, malathion or their metabolites

How does the administration of the poison tell you were it is most likely to be

• Look at the organs which it targets because that is where it will build up

• If a poison is ingestion (want to look at the GI tract for unabsorbed poison)

• If the poison is exerted in the kidney, there should be metabolites in the pee

• If the poison is inject must undergo first pass metabolism so may build up in the liver

• Immunoassays can detect metabolites if you suspect a drug

What would you look for if you suspect someone drink and took cocaine

Would look for cocaethylene

What does decomposition produce and how does it do that

Decomposition produces cadaveric alkaloids like putrescine and cadaverine via bacterial decarboxylation of amino acids ornithine and lysine

Phenylalanine is converted to phenylethylamine

Macromolecules also decompose vi a hydrolysis, oxidation and reduction that can obscures isolation, identification and quantitation of target chemicals

What levels can go up and down with putrefaction

Cyanide, ethanol and CO

What poisons are stable and can remain the body for years

arsenic, barbiturates and strychnine

What are kinda the primary screens done (2)

• Urine screen for ferric chloride, perchloric, nitric acid, FPN color test for phenothiazine drugs,

• immunoassays for amphetamines, benzos, opiate derivatives

What is standard additions and how do they work

involve adding known amounts of a suspected chemical to a preserved specimen (e.g. embalmed organ) and the results are compared to normal tissue

How can you tell what routes someone was administered the poison

• In general, highest concentrations = site administered; GI tract, liver = oral ingestion; Lungs = inhalation

• Ratio of relative distribution can determine it was oral or else

What happens when you smoke crack

Smoking introduces pyrolytic products of parent compound like smoking crack produces anhydroecgonine methyl ester

What is a con of urinalysis

is good for qualitative presence/absence, not cause of death

As some people react to different amount of poisons.

What physiological effects correlate with what

correlate with blood concentrations generally, which is the basis for therapeutic drug monitoring. Rather than urine levels

Why don’t people die imitate after given a poison

It takes time for a chemical to death and administration can allow redistribution, biotransformation and or exretion

How long does it tkae for for fatal acetaminophen to take place

Fatal acetaminophen OD takes 3-4 days so post-mortem blood acetaminophen is within therapeutic ranges

What is important to take into analysis of post-mortem analysis

If the individual went to the hospital they may have been treater with a drug so they may come up in the readigs

interpretations of toxicological findings

• Drugs are not evenly distributed in cadavers, nor do they maintain the same distribution patterns after death

• Site of the blood sample matter

What happens with drugs with high apparent volumes

They tend to have elevated blood concentrations over longer post-mortem intervals

Where are bloods normal taken

heart blood plus peripheral blood sample is taken