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
What does stomach contents measure?
Unabsorbed drug at the time of death
What is bile used for?
Identification purposes only
What can be identified in vitreous humour?
Alcohol (not drugs)
Advantages to vitreous humour
- Less subject to contamination and putrefaction
- Limited quantity available
- Clean sample
What can be identified in CSF?
Alcohol (can be used as a double check for blood alcohol)
What are some possible other samples not routinely taken?
- Kidney, brain, lung tissue
- Hair and fingernails
- Bone, heart, adipose tissue
- Sites of injection
Heroin can be detected in ____ tissue
Brain
Describe putrefaction
- Starts to occur immediately
- A time delay in bringing in exhibits may cause challenges w/ some analyses (ex: carbon monoxide, cocaine, alcohol, cyanide)
- Enzymes in the blood continue to break down cocaine even after death
- Freeze exhibits immediately if submission is going to be delayed
