Forensics 1 Flashcards
what is toxicology
analysis of body fluids and tissues for presences of drugs and poisons
3 areas of forensic toxicology
postmortem: cause of death
human performance: drugs/poisons modifying human behaviour or performance
forensic drug testing: determine drug use
knowledge required for a forensic toxicologist
drug metabolism
effects of poisoning on body
analytical chemistry
pharmacological action s
toxicology role in death
homicide suicide accident natural was there a drug, how much, when
does toxicologist determine cause of death
no pathologist does
answers if the amount was sufficient to cause death
info required to aid in interpretation in death
time and date of death details of last meal treated in hospital med history symptoms evidence at scene time delay between death and autopsy
what is postmortem redistribution
distribution of drugs from heart tssue to the cardiac blood
cardiac blood may be significantly elevated which may be good for preliminary investigations
changes start in 1h and usually done in 24hr
more accurate blood level sites
femoral and cardiac may allow for more accurate interpretation of blood level at time of death
some drugs that undergo postmortem redistribution
TCA
digoxin
info to aid interpretation in living person
signs and symptoms
admission of drug or alcohol use
evidence found at scene
4 stages of tox exam
- screen - for as many drugs as possble with as little samples as possible
confirm - 2 aliquots with different tests need to match
quantification - need to use blood, liver, stomach
interpret - toxic, therapeutic, lethal
improper specimen selection, collection, and submission =
inaccurate results
how to ensure continuity of exhibits
labelled by each possesser sent by courier adhesive tape to seal container kept under lock and key no access to lab to anyone unauthorized transfer slips used
types of blood samples and what they contain
serum
plasma - clotting factors
whole blood - RBC need to detect CO poisoning
most reliable sample for alcohol and drug impairment
blood
what is sodium fluoride
preservative to prevent breakdown of some drugs
benefits of urine sample
non invasive
little to no sample prep
drugs/alcohol found in higher concentrations here
longer detection periods
what is meant by urine having a long detection period
drug concentration that is detectable will be in the urine much longer than in the blood
disadvantages of urine
may not reflect level of impairment at time of incident - not quantitative
some drugs break down in body so detection difficult
subject to tampering
problems with cananbis detection in urine impairment vs probation
if used cannabis will be present in urine for long time
not able to convict someone of impaired driving but valid for someone who breached probation
urine sample uses
used for identification
cant determine when or how much drug was taken (can be used to determine BAC if period over which urine was collected is known)
if refuse to provide sample = guilty
hair sample advantages
noninvasive
easy to collect (crown of head)
no special storage requirements
useful in determining long term drug use
disadvantages of hair samples
not useful for alcohol detection
costly
can be affected by environmental contamination (smoking)
racial and hair color bias - drugs incorporates more into dark hair than light
not useful for acute
saliva collection method
expectorate into container
place cotton ball in mouth until saturated
may stimulate by chewing paraffin, rubber band, glass marble
advantages of oral fluid sample
noninvasive easy to collect no medical personnal required to sample drug detection time similar to blood only parent drug detected
disadvantages of oral fluid sample
requires sensitive analytical techniques
limited data regarding interpretation of oral fluid levels
recent smoking or oral consumption may complicate interpretation
advantages of sweat sample
noninvasice easy to collect with a patch patch impermeable to environmental contaminants tamper proof - has unique id number only parent drug detected (drug moves from body into patch)
disadvantages of sweat sample
costly
requires sensitive methods for detection
entire patch consumed in analysis so cant retest
limit info regarding incorporation of drugs in sweat and significance in findings - only really used for probation
samples used postmortem
blood urine liver stomach contents bile vitreous humor CSF kidnye brain lung hair and fingernails bone heart adipose tissue site of injection
explain blood collection post mortem
20ml from femoral and 20ml from cardiac
half of each sample in sodium fluoride to avoid breakdown of drugs and prevent formation of ethanol from bacteria
always whol eblood
often hemolyzed (RBC burst)
advantages of liver sample
most valuble
drug accumuates here up to 100x the amount in blood
liver may be only appropriate sample in
fire victims
babies
decomposed bodys
what info might you gather from stomach contents
drug OD by oral ingestion
may be able to identify undissolved tablets
measure of unabsorbed drug at time of death
corrosive agents if erosion of stomach lining
detects parent drug not metabolites
burnt almond smell =
cyanide
garlic smell -
pesticides
use for bile sample
waste product so just for identification not quantification
major route of elimination for some drugs - opiates, methadne, benzo
what is vitreous humor used to detect
for alcohol when blood isnt good
not used for drugs
advantages of vitreous humor sample
sterile environment so more true concentration
no putrefaction
clean sample
disadvantage of vitreous humor sample
limited quantitiy
when is CSF used
for alcohol when available
less subject to putrefaction and contamination
clean sample
dis of CSF
limited quantity
diffficult to collect - spinal tap
use kidney sample when
metal poisoning suspected
use lung sample when
inhalation of poison
samples less likely to use unless there is not a lot left to sample or unknown cause
kidney brain lung tissue hair and fingernails bone heart adipose tissue sites of injection
when does putrefaction occur and how to prevent
right away
freeze them
carbon monoxide putrefaction
products interfere with analysis bc same UV spectrum
cocain putrefaction issues
enzymes in blood continue to break down cocaine so then converted to inactive metabolite
alcohol putrefaction issues
bacteria produces alcohol
cyanide putrefaction issues
bacteria produce cyanide post mortem
