Blood and Body Fluids Flashcards
What are the common types of body fluids in crime scenes?
Blood
Semen
Saliva
What are the less likely types of body fluids examined at a crime scene?
Sweat
Urine (toxicology)
Faeces (bacterial_
What does a crime lab do?
Presence of body fluids, blood pattern analysis (preliminary testing)
What circumstances is blood analysis used?
Assault/murder, injury to suspect (blood pattern analysis)
What circumstances is semen analysis used?
Sexual assault
What circumstances is saliva analysis used?
Sexual assault
Bites
Saliva on mask
How is blood extracted from a sample?
Rub filter paper
How is semen and saliva extracted from a sample?
Damp blotting paper
What is the initial Characterisation of blood?
Sample blood?- preliminary tests i.e. luminol test
Sample animal blood? i.e. precipitant test
Animal blood, what species i.e. anti-serum
Human blood- what type?
Sex (chromosome testing, testosterone), age and race of source (clotting crystallisation)
What are the preliminary tests for blood for Leuchomalchite Green?
LMG (reduced) –Test stain +H2O2-> LMG (oxidised)
Colour change to blue/green
Hydrogen peroxide
What are the preliminary tests for blood for Kastle Meyer?
Phenolphthalein (reduced)-Test stain +H2O2-> Phenolphthalein (oxidised)
What are the preliminary tests for blood for Luminol?
3-aminophthallyhydrazide
Chemiluminescence in the presence of Hb
Luminol + H2O2 -> 3-aminophthalate (light producing reaction)
Shows hidden crime scenes i.e. may not have seen blood present, luminol highlights this
Nothing vanishes without a trace
Discovery can lead to more evidence i.e. blood soaked through carpet, provides more sample
Problems- luminol can lead to destruction of other evidence e.g. footprints and fingerprints
Thinks like bleach and saliva can provide a false positive
What is microscopy used for in testing semen?
Large amount of DNA present, treat with staining reagent, high power microscopy
How long is semen present after an incident?
5 days
What does Acid Phosphatase do in the presence of semen?
Purple colour is produced, also present in vaginal fluid (small quantities)
What is the preliminary testing for saliva?
Starch/Iodine- turns blue/black in present of starch
Salivary Amylase- saliva breaks down starch (no blue/black colour) broken down to monosaccharides
Saliva may contain bacterial/cheek cells (DNA profiling)
What does blood pattern analysis analyse?
Examination of shapes, location and distribution of blood stains, in order to provide an interpretation of the physical events which gave rise to the origin
How can blood pattern analysis provide information regarding sequence of events?
Position of the victim
Evidence of struggle
How can blood pattern analysis provide evidence to corroborate or refute statements made by those involved?
Stain patterns on suspects clothing
Stain patterns on victim/ at scene
What are the types of patterns?
Passive
Transfer
Projected
What is Passive patterns?
Due to gravity Drops Drips Pools Clots Shape affected by target surface texture Smooth vs. rough surfaces
What is Transfer patterns?
Wet bloody surface in contact with another surface produces a pattern Contact Swipe/smear Wipe Smudge
What is Projected patterns?
Arterial spurt/gush- blood exiting at high pressure & velocity
Cast of stains- comes from weapon, goes in an ark
Impact: low, medium, high velocity
Point of convergence- point of impact, where victim may have been lying
What is the importance of blood grouping?
Still used in many countries
Historical cases
Large samples eliminated by quick inexpensive screening
Discovery of more systems inherited independently of each other and ABO- particular crime suspect type A other blood types can be ruled out
What are the immunological systems?
Protein variants
Groups
Elimination
Increase typing systems-decrease the number of people sharing the combination
Quantity of blood may be limited- limited analysis
Analysis time consuming
What are the Immunological biological markers?
ABO Rhesus MNS Duffy Km
What are the protein biological markers?
ACE (Acetylcholine Esterase)
ACP (Acid Phosphatase)
Haemoglobin
PGM (Phosphoglucomutase)
What antigens are present in people with blood type A?
A
What type of antibodies are present in the serum in blood type A?
Anti-B
What antigens are present in people with blood type B?
B
What type of antibodies are present in the serum in blood type B?
Anti-A
What antigens are present in people with blood type AB?
AB
What type of antibodies are present in the serum in blood type AB?
Neither anti-A or anti-B
What antigens are present in people with blood type O?
Neither A or B
What type of antibodies are present in the serum in blood type O?
Both anti-A and anti-B
What are examples of blood proteins?
Polymorphines
Iso-enzymes
E.g. Hb- sickle-cell anaemia
Probability
What percentage of the population are secretors?
75-85%
What do secretors have?
Higher concentration of A and B antigens
