7 - Forensics Overview Flashcards
What is the definition of toxicology?
Analysis of body fluids and tissues for presence of drugs and poisons
3 areas of forensic toxicology
- Post-mortem forensic toxicology (cause and manner of death, analysis of body fluids and tissues)
- Human performance forensic toxicology (modifying human performance or behaviour, analysis of blood/ breath/ urine)
- Forensic drug testing (determine drug use, analysis of urine/ oral fluid/ sweat/ hair)
What questions must a forensic toxicologist be able to answer?
- Was a drug/ poison found?
- What was it?
- How much was found?
- Was the amount of poison/ drug sufficient to cause death (ex: murder, poisoning) or impairment (ex: impaired driver)?
- When and how was the poison/ drug taken into the body?
What information is required to aid in the interpretation when a death has occurred?
- Age, gender, weight
- Time and date of death/ incident
- Details of last meal; actions between meal and onset of sx
- Was person treated in hospital? (if so, what drugs were given in hospital?)
- Medication and drinking hx
- Sx prior to death
- Pathologist’s findings/ observations
- Evidence found at the scene
- Health of deceased (any prior medical conditions?)
- Time delay between death and autopsy (post-mortem redistribution)
Describe post-mortem distribution. What is required for an accurate interpretation?
- Involves the distribution of drugs from the heart tissue to the cardiac blood
- Majority occurs in the first 24 h post-death
- Cardiac blood levels may be significantly elevated (up to 10x)
- Levels from 2 sites (femoral and cardiac) allow for more accurate interpretation
- Use the cardiac sample for the screen; use femoral sample for quantification
What information is required to aid in the interpretation when the investigation involves a living person?
- Age, gender, weight
- Signs and sx of impairment or intoxication
- Admission of drug and alcohol use
- Evidence found at the scene or on the victim or accused
What type of sample is used for quantification?
- Best = blood
- 2nd best = liver
What are the 3 types of blood samples?
- Serum (no clotting factors)
- Plasma (has clotting factors)
- Whole blood (has cells)
___ is the most reliable sample for interpretation of alcohol and drug impairment
Blood
How do you preserve blood?
1% sodium fluoride
Advantages to urine
- Non-invasive and convenient to collect
- Little or no sample prep (don’t have to remove any cells or lipids from urine like you would w/ blood)
- Drugs/ alcohol found in higher concentrations
- Longer detection periods compared to blood
Disadvantages to urine
- May not reflect level of impairment at time of incident
- Some drugs break down in body, making identification more difficult
- May be subject to adulteration or tampering
What is urine used for?
- Identification purposes
- Exception -> can be used to estimate BAC if period over which urine was collected is known
Advantages to hair
- Relatively non-invasive
- Easy to collect
- No special storage requirements
- Useful in determining long-term drug use
Disadvantages to hair
- Not useful for detection of alcohol
- More costly than urinalysis
- Environmental contamination may be an issue (so must wash the outside of the hair and only analyze what is inside the hair)
- Potential for racial and hair colour bias (drugs incorporate into darker hair preferentially than lighter hair)
Describe the collection method of oral fluid/ saliva
- Expectorating into a container or placing a cotton swab or gauze in the mouth and allowing the oral fluid to be absorbed over a period of time or until saturated
- Stimulation of oral fluid may involve chewing on a piece of paraffin, rubber band or glass marble
Advantages to oral fluid/ saliva
- Non-invasive and easy to collect
- No medical personnel required to collect samples
- Drug detection times similar to blood
Disadvantages to oral fluid/ saliva
- Only parent drug detected
- Requires sensitive analytical techniques
- Limited data regarding interpretation of oral fluid levels
- Recent smoking or oral consumption may complicate interpretation
Advantages to sweat
- Non-invasive and easy to collect
- Patch impermeable to environmental contaminants
- Each patch has unique ID #; tamperproof
Disadvantages to sweat
- Only parent drug detected
- Costly
- Requires sensitive methods for detection
- Entire patch is consumed in analysis
- Limited info regarding incorporation of drugs in sweat and significance of findings
When are sweat samples generally used?
Breach of probation cases
What samples can be collected from a deceased patient?
- Blood, urine
- Always get hemolyzed whole blood (hemolyzed = cells have burst)
- Sometimes urine not available after death
- Liver
- Stomach contents
- Bile
- Vitreous humour
- CSF
____ is one of the most valuable tissues for post-mortem drug analysis
Liver
When are stomach contents analyzed?
Where drug overdose by oral ingestion is suspected
