bodily fluids: Flashcards
bodily fluids:
excreted- dispelled as waste from the body: faeces, vomit, urine.
secreted- transferred from one area of the body to another: sweat, blood/plasma, semen, saliva.
bodily fluids help determine how/when a victim died and who the offender was.
forensic pathology:
cause, manner and time since death.
eg- diatoms in the pleural liquid (liquid barrier around the lungs), stomach contents/vomit analysis, estimating time since death using vitreous humour (liquid in eye).
detection:
many fluids and stains are invisible. screening techniques can be used- alternative light sources (ALS), chemical agents (luminol, test for presence of blood). locate fluids in situ before collection.
forensic approach:
- presumptive test- indicate potential source.
- confirmatory tests- conclusively identify type of biological material.
- downstream analyses- individualise (DNA).
tests: vary by type of fluid, non destructive, scene based/lab based and avoid contamination.
blood:
most common bodily fluid encountered. volume recovered varies- drop, stain, pattern. detectable after cleaning attempts.
various presumptive tests available.
bloods nature:
viscous- 3-4x thicker than water.
55% plasma- water, antibodies, proteins, enzymes, hormones, amino acids, glucose and inorganic substances- drugs/alcohol.
45% cellular material.
blood function- erythrocytes:
RBCs, most common (44%).
contains haemoglobin (iron containing protein carries o2 and co2).
blood its colour. its shape allows it to be flexible for travel (no nucleus).
antigens on surface of RBCs which gives blood type characteristics.
blood function: leucocytes
WBCs. <1% blood volume. contain nuclei (DNA).
protect against infectious disease and invaders.
5 types of WBCs- granulocytes (neutrophils, eosinophils, basophils), lymphocytes, monocytes.
blood function- thrombocytes:
platelets and cell fragments. irregularly shaped, colourless- produced in bone marrow.
sticky surface which form clots to stop bleeding.
fluidity of the blood.
active when circulatory system walls damaged.
blood types:
classification of blood based on presence/absence of antibodies (plasma) and inherited antigenic substances (RBCs).
blood type inherited from both parents.
2 important systems- ABO and RhD.
ABO system:
denotes presence of 1, both, or neither A or B antigens on RBCs.
initially discovered by Landsteiner (1901).
4 main groups- A, B, O, AB.
phenotypes vary in different populations.
rhesus (Rh) system:
2nd most important blood group system.
50 defined blood groups including D, C, c, E.
initially discovered in monkeys by landsteiner and weiner (1930s).
RdH antigen- important and most immunogenic (+ present) (-absent).
84% of europeans RhD+ (A+, B+, O+, AB+)
AB(O)H secretors:
person secretes antigens into bodily fluids- saliva, urine, tears, bile, digestive fluids.
80% of caucasian population carry gene.
forensic importance- blood group established from other fluids, exclusion of non secretor, useful historically.
bloods forensic significance:
RBCs- identify blood group antigens, peroxidase like activity= detection.
WBCs- DNA analysis.
plasma- serum (species testing), drug/alcohol screening, BPA.
blood pattern analysis (BPA):
blood exits the body as a liquid.
exits differently depending on injury/action- flow, drip, spray, spurt, gush, ooze.
analysis of patterns- what happened/order of events.
- active bloodstains
blood travels by force other than gravity. impact to the body (weapon)- spatter. projection (punctures artery)- gushes or spurts. secondary object (weapon)- cast of stains.
direction of travel on impact- tails.
angle of impact- round/elongated.
- passive bloodstains
blood formed solely under influence of gravity.
blood flows often extensive- body position, has the body been moved post mortem
droops and pools= time since bloodshed- estimate drying time. angle of impact.
- transfer bloodstains
blood deposit= direct contact with contaminated objects.
from weapon or person (hand/footprints), disposing of evidence (wiping a weapon on clothing), indicate repeated contacts.
presumptive tests:
determine presence of trace levels, following clean up, tests unknown stains at crime scene and in lab.
presumptive tests: screening techniques
ALS/chemiluminescence (non visible traces)- polilight, luminol, flourescin, bluestar.
informs use of additional presumptive tests, rapid and non detsructive.
ALS used to detect variety of fluids.
luminol- relies on haemoglobin reacting to peroxidase through interaction with hydrogen peroxide in the luminol- most effective
presumptive tests- catalytic tests:
haemoglobin catalyses oxidation of reagents (h2o2)- changes colour if positive.
phenolpthalein (kastle meyer test- blood+ ethanol+ KM reagent+ hydrogen peroxide= pink) and leucgomalachite green (LMG).
will detect tiny amounts of blood but potential for false positives (things with iron in).
confirmatory tests:
absolutely identify unknown stain as blood. microscopic assessment of RBCs and WBCs.
crystal tests- teichman and takayama- formation of hematin/hemochromogen= crystals.
spectroscopy highly reliable- haemoglobin derivatives (soret absorbance band).
serological tests:
precipitin test= identify human proteins- does haemoglobin in blood react with anti human haemoglobin, repeat tests using antiserums for other species.
further forensic analysis on blood type- reaction of antisera with blood antigens.
associate/exclude individuals.
saliva:
non invasive control sample collection.
forensic analysis- identify the accused, detect drugs/alcohol, poisoning cases, hormone levels, species identification- animal bites
salivas nature:
digestive aid- breaks down food starches. produced by 3 main glands (sublingual, submandibular, parotid) serous and mucus cells.
humans produce 1-1.5L a day.
99% water with pH of 6.8-7. 1%electrolytes, immunoglobulins, proteins, enzymes, nitrogenous products, WBCs, including digestive enzyme- alpha amylase.
saliva function:
lubrication and cleansing of the mouth. aids digestion- broken up food= bolus, solubilise dry food, alpha amylase breaks down starch, salivary lipase digests fat.
anti microbial properties- lysozyme.
maintains oral hygiene.
forensic analysis of saliva:
few well known and accepted presumptive tests- enzymatic methods. ALS screening.
saliva- enzyme analysis:
saliva ID based on presence of amylase enzyme- phadebas, SALIgAE, RSID.
sample of stain added to soluble starch solution, iodine added as reagent. not specific for human saliva.
high false positive rate.
looking for no reaction as it means that starch is still present, so it hasn’t been digested so alpha amylase isn’t there. looking for a negative test.
semen:
evidence in sexual offence cases- person (clothing, swabs, combings, hair, blood) scene(condoms, bedding, furniture).
speed is important- medical exam of victim: detecable up to 31 hours in the mouth, 44hrs in the anus, 10 days in the vagina and 19 days in the cervix.
complex fluid and cellular mixture produced by male reproductive glands.
semen nature:
- cellular mixture= spermatozoa- reproductive cells carry genetic material for sexual reproduction.
- complex fluid= seminal fluid, protective, nutrient rich environment for sperm cells post ejaculation.
15-20% from the prostate. proteins including acid phosphate, prostate specific antigens and albumin.
5% from epididymis and testis. sperm rich fluid.
60-75% from seminal vesicles. hormones, proteins (coagulants, fructose, glucose)
semen function:
sexual reproduction.
contributes half of genetic information to offspring.
average ejaculate 2-6ml- 100-150 million sperm cells per ml. alkaline pH 7.2-7.6.
semen forensic analysis: presumptive tests.
ALS- but not all semen fluoresces.
test for seminal acid phosphatase (sSAP0 most common. if present, AP will react with alpha naphthyl phosphate.
detect PSA (prostate specific antigens). present in seminal plasma= antibody antigen-reactions.
semen forensic analysis: confirmatory tests
microscopic ID of sperm cells. treated with stain to visualise heads. christmas tree stain- nuclear fast red- nuclei, picriondigocarmine- tails (green).
RS-ID semen strip test. sensitive and specific. seminal vesicle- specific antigen- semenogelin, pre ejaculation fluid also.
vaginal fluids:
not as common at crime scenes.
important role in sexual assault cases.
very few tests as fluid is not well defined- composition varies due to menstrual cycle and variable hormone levels.
over a month, vaginal fluid will have different viscosity, different hormones and different proteins.
vaginal fluid nature and function:
vaginal secretions= mucus or fluid produced from cervical and vaginal glands.
average production is 6g a day.
protects from microbial/bacterial infections.
proteins include lysozyme, acid phosphate, amylase.
shed blood cells, urea, epithelial cells.
vaginal fluid presumptive tests:
no presumptive/confirmatory test routinely used.
detect glycognated epithelial cells with periodic acid-schiff (PAS) reagent- stains cytoplasm magenta.
lactic (vaginal)/citric acid (semen) ratio- VF or semen?
only been positively used on women who menstruate- unsuccessful on prepubescent or post menopausal women. not routinely used.
menstrual fluid:
need to distinguish between peripheral and menstrual blood. important in context- trauma or natural bleeding.
immunochromatographic assays to detect degradation products of fibrinolysis (FDPs)- D-dimer most significant FDP subtype. menstrual blood 200x greater D-dimer than peripheral. D-dimer assays effective in detecting menstrual blood.
menstrual fluid 2:
SERATEC-PMB- detect haemoglobin and d-dimer. preserves DNA.
forensic validation- specific and sensitive. (3um), different treatment time based on age of sample, no false +ves or -ves (age, mixtures), post moretem +ve samples, DNA extracted- sample buffer and sample well, successfully applied to case work samples.
urine:
useful in sexual assault.
difficult to detect- low intensity of available tests, false positive results.
less viscous than other fluids- dispersal, dilution.
odour not localised.
urine nature and function:
liquid by product of the metabolism.
expels nitrogen rich by products- urea, uric acid, creatinine.
average production- 1.4L a day.
91-96% water- inorganic salts and organic compounds (proteins, hormones, metabolites), solids.
urine forensic tests:
diluted urine- limited ALS detection
urea- activity of the enzyme urease. breaks down urea, releases ammonia and co2. detect ammonia via nesslers pr DMAC reagent.
crratinine: high concentrations. jaffe test= creatinine reacts with picric acid in alkaline medium.
RSID urine test:
tamm-horsfall (THP) most abundant protein- 50-200mg a day excreted. specific to urine but concentration varies. blood inhibits urine detection and not human specific.
sweat:
least common bodily fluid found at crime scenes.
DNA evidence- extracted from hats, clothing, bedding.
sweat nature and function:
fluids secreted by sweat glands in skin.
means of thermoregulation.
sweat rates up to 2-4 an hour or 10-14L a day.
mostly water with dissolved mineral traces- lactic acid, urea, creatinine, Na, K, Ca, Mg.
sweat forensic tests:
most difficult bodily fluid to identify.
1. SEM-EDX: chlorine peak basis of comparison.
2. G-81: monoclonial antibody (sweat specific) ELISA analysis.
3. metabolite biometrics: single-analyte enzymatic assays distinguish persons.
additional forensic intelligence- drug use, alcohol consumption.
forensic value of bodily fluids
fluids important for context of case- source. downstream DNA analysis- enables robust identification.
fast, efficient, inexpensive- saves time, money, effort.
allows sorting of evidence by relevance
bodily fluids analysis a major component of crime scene and lab processing.
proteomics:
protein analysis within bodily fluid testing.
proteome: proteins coded in genetic makeup of individual (genome). study of all proteins in a cell (structure, modifications, interactions), changes with environmental conditions.
may yield detailed profile of an unknown individual.
