Summary Summery Forensic Toxicology

FORENSIC TOXICOLOGY
LECTURE 1: INTRODUCTION & SPECIMEN ISSUES
- Toxicology  study of harmful interactions between substances and biological
systems.

What is forensic toxicology
 A specialization of human toxicology. ‘the application of toxicology for the
purposes of the law’
- Forensic toxicology is part of forensic medicine:
 Forensic pathology
 Forensic toxicology
 Forensic anthropology
 Forensic odontology

Where is forensic toxicology applied
- Criminal law:
 (fatal) poisoning
 Overdose
 Drink & drive
 Were drugs taken
- Civil law:
 Exposure to harmful substances in the workplace
 Error in medical treatment
- Doping in sports:
 Did the athlete use banned substances

Difference between medical and forensic tox/drug testing
- Medical:
 Patient consent not required.
 Identity of specimen is presumed.
 Screening result is sufficient for medical decision.
 Analyte is known.
 Results are used for medical evaluation.
- Forensic:
 Legal basis for testing of subject / subject must consent to be tested.
 Identity of specimen must be proved (“chain of custody”)
 Only confirmed results can be considered positive (“confirmation of
molecular structure”)
 Analyte is not known (“screen first”)
 Results are used for legal action.

What is examined in a forensic toxicology case
- Investigation of: poisoning deaths, poisoning of the living, forensic drug testing.
- Occupational applications: enforcement of legal exposure limits, to ensure safe
water air and food.




Components of a forensic toxicology case
- Case history:

,  Context, evidence collected at crime scene.
 Bottles, pill, powders, trace residue, available chemicals.
 To narrow the search.
- Analytical determinations
 Chemical and biomarkers
 That’s your job  find the best analysis to answer the toxicological
questions in a case.
- Toxicological interpretation
- And presentation of results.




Toxic issue and death




Toxicological questions to be answered
- Was death of illness due to a poison?
- What toxin produced the illness?
- Was the substance employed capable of producing death?
- Was a sufficient quantity taken to produce death or toxic results?
- When and how was the toxin taken?
- May a poisoning have occurred and the poison either be or have become
undetectable?

, - Could the detected poison have an origin other than the poisoning?
- Was the poisoning SUICIDAL, ACCIDENTAL or HOMICIDAL?
- Were the correct specimens collected and preserved, analyzed in such a manner
to answer the question at hand?

SPECIMEN
Why are these samples analyzed?
 To obtain qualitative and quantitative information on the presence of harmful/
banned substances.
 Qualitative: absent or present? Identity of poison/ drug.
 Quantitative: how much? Dose.
- The results will help the toxicologist to interpret:
 Physiological effects (at time of crime)
 Behavioural effects (at time of crime)

What kind of samples (specimen) are examined in forensic toxicology
- Biological samples: blood, urine, oral fluid, gastric/ bowel content, eye fluid
(vitreous humor), sweat, breath, hair, nails, bile, lung, brain, liver, kidney, bone …
- Exhibits (from crime scene/ ante mortem): food and drinks, glasses and plates,
syringes, needles.
- Medication / drugs.

Urine
- Produces by the kidneys.
- Blood filtration by the kidneys.
- Stored in the bladder until voided – collect from bladder.
- Many drugs and metabolites are present at higher concentrations in urine that in
blood.

Bile
- Digestive secretion.
- Continuously produced by the liver.
- Stored in the gallbladder.
- Certain drugs can be concentrate in the bile.
Qualitative – the presence of a drug in the urine/ bile of an individual indicates that some
time prior to death the drug of poison was present in the blood of the individual.

Vitreous humour
- Fluid that occupies the space between the lens and the retina of the eye.
- Sequestered from putrefaction, charring and trauma, micro-organisms.
- Useful in cases where decomposition is advanced, body is exhumed or in fire
deaths.
- Limitation- blood:vitreous ratio may not be known.

Stomach contents
- Visual examination may reveal tablets.
- Drugs that have been orally ingested may be detected in stomach contents.
- Generally qualitative:
 Stomach contents are not homogeneous.
 Only a portion of stomach contents collected.
 Useful for directing further analysis.
Post mortem blood