4104 - forensic science > bodily fluids > Flashcards

bodily fluids Flashcards

(59 cards)

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1
Q

what are bodily fluids?

A

liquids ex/secreted by or present within the body

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2
Q

what bodily fluids are ex/secreted?

A

excreted - vomit, faeces, urine

secreted - saliva, semen, blood/plasma

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3
Q

what are the forensic applications of bodily fluids?

A
  • fluids within the human body
  • fluids transferred to the victim/scene
    help forensics determine
  • how/when a victim died
  • who the offender was
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4
Q

how can bodily fluids be used in forensic pathology?

A

cause, manner and time of death

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5
Q

how are bodily fluids of forensic value?

A

present at various crime scenes
persistence over time
detection+identification = DNA analysis

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6
Q

detection of bodily fluids

A

many fluids and stains invisible
screening techniques at scene
- alternative light sources
- chemical agents
locate fluids ‘in situ’ before collection

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7
Q

what is the forensic approach to bodily fluids?

A

presumptive tests
confirmatory test - conclusively identify type of biological material
downstream analysis - individualise - DNA

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8
Q

collection of bodily fluids

A

from the scene, evidence or person
- documentation
- swabs, tapes, cuttings
comparison samples - controls
measures to avoid cross contamination

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9
Q

what is the most common bodily fluid encountered?

A

blood

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10
Q

what are the forensic uses of blood?

A

reconstruction
- who was involved
- what happened
- when did it happen
- what evidence is needed from suspect

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11
Q

how much thicker is blood than water?

A

3-4 times

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12
Q

what is blood composed of?

A

55% plasma
45% cellular material

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13
Q

what are the parts of the plasma?

A

91% water
7% blood proteins
2% nutrients, hormones, electrolytes
also has inorganic substances - drugs, alcohol

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14
Q

what are the parts of the cellular component?

A

buffy coat - white blood cells and platelets
red blood cells

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15
Q

what gives red blood cells their blood-type characteristics?

A

antigens on the surface

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16
Q

what do leucocytes contain that is important?

A

DNA

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17
Q

what is the purpose of thrombocytes?

A

sticky surface to form clots to stop bleeding

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18
Q

what are the 2 important systems with red blood cells?

A

ABO
RhD antigen

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19
Q

ABO system

A

denotes presence of one, both or neither A/B antigens
discovered in 1901

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20
Q

what are the 4 main groups of blood types?

A

A
B
AB
O

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21
Q

Rhesus system

A

RhD antigen - important and most immunogenic
present +
absent -

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22
Q

importance of AB(O)H secretors?

A

blood group established from other fluids
exclusions of non-secretor
useful historically

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23
Q

forensic significance of RBCs, WBCs, Plasma?

A

RBCs
- identify blood group antigens
- peroxidase-like activity = detection

WBCs
- DNA analysis

Plasma
- Serum (species testing)
- drug/alcohol screening
- BPA

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24
Q

Blood pattern analysis

Study These Flashcards
A

blood exits body as a liquid
exits differently depending on injury/action
analysis of pattern - what happened / order of events

25
active bloodstains
blood travels by force other than gravity - impact to body - spatter - projection - gushes/spurts - secondary object - cast off stains direction of travel on impact angle of impact
26
passive bloodstains
blood formed solely under influence of gravity - drops/pools = time since bloodshed - blood flows often extensive - body position, has body been moved since death angle of impact
27
transfer bloodstains
blood deposit = direct contact with contaminated objects - from weapon or person - disposing of evidence - indicate repeated contacts
28
presumptive tests
determine presence - trace levels - following clean up - test unknown stains - at crime scene and in lab
29
what are the 2 types of presumptive testing for blood?
- screening techniques - catalytic tests
30
screening techniques
ALS/chemiluminescence for non-visible traces informs use of additional presumptive testing rapid + non-destructive
31
catalytic tests
haemoglobin catalyses oxidation of reagents - changes colour if +ve phenolpthalein & leuchomalachite green will detect tiny amounts of blood but potential for false positive
32
what is the colour for a positive result with KM for blood?
pink
33
steps for KM test?
blood + ethanol + KM + hydrogen peroxide
34
confirmatory tests
microscopic assessment of RBCs and WBCs crystal tests spectroscopy highly reliable
35
serological tests
precipitin test =identify human proteins further forensic analysis on blood type associate/exclude individuals
36
forensic purpose of saliva?
identify the accused detect drugs/alcohol poisoning cases hormone levels species identification - animal bites
37
what is saliva made of?
99% water - pH 6.8-7.0 1% electrolytes
38
function of saliva
lubrication and cleansing of the mouth aids digestion anti-microbial properties maintains oral hygiene
39
forensic analysis methods of saliva?
enzymatic reactions ALS screening
40
enzyme analysis of saliva
saliva ID is based on presence of amylase enzyme sample of stain added to soluble starch solution, iodine added as reagent
41
disadvantages of enzyme analysis for saliva
not specific for human saliva high false positive rate
42
aim of semen forensically?
identify/exclude a suspect
43
cellular mixture of semen
spermatazoa
44
complex fluid of semen
seminal fluid - protective, nutrient rich environment for sperm cells, post cum 15-30% from prostate 5% from epididymis and testis 60-75% from seminal vesiclesf
45
function of semen
sexual reproduction average ejaculate 2-6ml alkaline 7.2-7.6pH
46
presumptive test for semen
ALS - but not all semen flouresces test for seminal acid phosphatase detect phosphate specific antigens
47
confirmatory tests for semen
microscopic ID of sperm cells - treated with stain to visualise heads -- nuclear fast red (nuclei) or picroindigocarmine (tails) - RS-ID semen strip test - sensitive&specific, also pre cum
48
nature/function of vaginal fluid
vaginal secretions - mucus/fluid produced from cervical&vaginal glands average 6g/day protects from microbial/bacterial infections
49
presumptive tests for vaginal fluids
only presumptive test is for detecting glycogenated epithelial cells with Periodic Acid-Schiff reagent stains cytoplasm magenta
50
what is the identifying part to menstural blood?
D-dimer that is FDP subtype
51
what detects haemoglobin and d-dimer in menstrual blood?
SERATEC-PMB
52
disadvantages of urine analysis
difficult to detect - low sensitivity of available tests, false positives less viscous than other fluids - dispersal/dilution
53
nature&function of urine
expels nitrogen rich by products - urea, uric acid creatinine average 1.4L produced per day 91-96% water
54
forensic tests of urine
limited ALS detection urea - activity of enzyme urease creatinine - high conc use Tamm-Horsfall (THP) antibodies test for most abundant protein THP
55
forensic advantages of sweat
allows for DNA analysis
56
nature & function of sweat
secreted by sweat glands in the skin up to 2-4L/hour or 10-14L/day mostly water with dissolved minerla traces
57
forensic tests for sweat
SEM-EDX - chlorine peak basis of comparison G-81 - monoclonal antibody ELISA analysis Metabolite biometrics - single analyte enzyme assays
58
precipitin test
tests blood to see if it is human or animal blood
59
leuchalamite green
test for blood
4104 - forensic science
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