This document provides an overview of the examination and forensic value of blood evidence. It discusses the history and principles of forensic blood analysis, the nature and composition of blood, blood grouping techniques, and how blood evidence can be analyzed to determine factors like the species, sex, race and age of the source. It also addresses how blood evidence can provide information about the nature of a crime based on whether the blood is wet or dry, and how blood spatter patterns and locations can reveal details about the position and movements of victims and suspects.

1. Examination of
Blood
By : Gan Quan Fu, PT,
MSc. Human Anatomy (Batch 3)

2. Content
• Introduction
o History
o Locard’s Exchange Principle
o Blood Evidence
o Forensic Value of Blood
• Nature of Blood
o General Characteristics
o Roles
o Red Blood Cells
o Serum
• Blood Grouping
• Individualization of Blood
• Blood Analysis
o General Question
o Screening Test
o Determination of Sex, Race and Age
• Crime Scene
o Wet VS Dry Blood
o Nature of Crime
o Cause of Death
o Blood Splashes
• Collection of Blood Stain
• References

4. History
Prof. Dr. Edmond Locard
o (13 Dec. 1877 – 4 May 1966)
o Pioneer in forensic science who
became known as Sherlock
Holmes of France.
o Formulated the basic principle
of forensic science: "Every
contact leaves a trace".
o Became known as Locard's
exchange principle

5. Locard’s Exchange Principle
“ Wherever he steps, whatever he
touches, whatever he leaves, even
unconsciously, will serve as a silent
witness against him. Not only his
fingerprints or his footprints, but his hair,
the fibers from his clothes, the glass he
breaks, the tool mark he leaves, the
paint he scratches, the blood or semen
he deposits or collects. All of these and
more, bear mute witness against him.
This is evidence that does not forget. It is
not confused by the excitement of the
moment. It is not absent because
human witnesses are. It is factual
evidence. Physical evidence cannot
be wrong, it cannot perjure itself, it
cannot be wholly absent. Only human
failure to find it, study and understand it,
can diminish its value”
- Professor Dr. Edmond Locard

6. Blood Evidence
• Most well-known and significant
evidence in modern criminal
justice system. Because:
o It can link a victim to a suspect
(via Locard’s Exchange
Principle).
o Bloodstain patterns reveal
great deal about position and
movement during crime.
o It managed to destroy self-defense
arguments of suspects.
• There's no substitute for it, whether
for medical or forensic purposes.

7. Forensic Value of Blood
• Blood has always been
considered class evidence in
forensic Science.
• Individualized blood evidence is
possible in the near future.
• In some cases, forensic
serologists were able to link a
single perpetrator to a
bloodstain with strong
probability estimates.

9. General Characteristics
• Slightly alkaline fluid
• Circulates throughout our bodies, nourishing our
cells, transporting oxygen and waste.
• Fluid portion of blood consists of plasma and serum .
• Non-fluid portion consists of red blood cells which
outnumber white cells by five hundred to one
• Blood is composed of:
o Water
o Cells
o Enzymes
o Proteins
o Other inorganic substances

10. Roles
• Medical scientists are more interested in
white cells.
• Forensic scientists are more interested in red
cells and secondly serum.

11. Red Blood Cells
• Most prevalent blood cells in
the human body.
• Deliver oxygen from the lungs
to the body’s tissues.
• Forensic analyst search for
smaller chemical substances
residing on their surfaces (ie.
antigens), which also tend to
have important forensic
implications.

12. Serum
• Characterized by its yellow hue,
and contains white blood cells and
platelets.
• Forensic analysts able to determine
the freshness of a blood sample by
examining serum (it clots several
minutes after exposure to air).
• A centrifuge can be used to
separate the clotted material from
the serum portion.
• Serum contains antibodies , proteins
floating in blood fluid, which have
significant forensic implications.

14. Blood Grouping
A-B-O system of blood typing was discovered
in 1901 by Dr. Karl Landsteiner, an Austrian
biologist and physician. (June 14, 1868 – June
26, 1943)
o Developed the modern system of
classification of blood groups from his
identification of the presence
of agglutinins in the blood.
o 1909  Discovered polio virus.
o 1930  Received Nobel Prize in
Physiology or Medicine.
o 1937  Discovered Rhesus factor.
o 1946  awarded a Lasker Award and is
recognised as the father of transfusion
medicine.

15. Blood Grouping
• Late 1930s, a series of antigen-antibody
reactions discovered in
blood, the most common ones
being ABH, MN, Rh, and Gm
(gamma glouburin marker).
• There are more than 256
antigens, and 23 blood group
systems based on association
with these antigens.
• A fundamental principle of
serology is that for every antigen,
there exists a specific antibody.
• All blood groups are defined by
the antigens on their red blood
cells and the antibodies in their
serum.

16. • ABO blood group antigens present
on red blood cells
• IgM antibodies present in the serum.

18. Blood Typing
• Blood typing requires 2 antiserums:
1. anti-A
2. anti-B.
• Insert a droplet of these antiserums in samples of blood can
determine which samples maintain normal appearance and
which become clotted, or agglutinated under microscopic
examination.
‘A’ blood agglutinated by
anti-A serum.
‘B’ blood agglutinated by
anti-B serum.
‘AB’ blood by both.
‘O’ blood by neither.

19. Rhesus Factor
• Can be categorized using Rh
(Rhesus disease) factor.
• Positive Rh factor, means the
blood contains a protein that is
also found in Rhesus monkeys.
• Approximately 85% of the
population has a positive Rh
factor.
• The Rh factor, like other
antigens, can be found on the
surface of red blood cells.

21. Individualization of Blood
• Potential for the individualization
of blood is based on the typing
of proteins andenzymes.
• Blood proteins and enzymes
have the quality of being
polymorphisms or iso-enzymes,
which means they exist in several
forms and variants.
• Most people are familiar with at
least one common
polymorphism in blood: Hb,
which causes sickle-cell anemia.

22. Secretors
• 1925  Blood-related discovery valuable to forensic
science was made.
• Approximately 80% of the human population was found
to be "secretors” individuals whose specific types of
antigens, proteins, antibodies, and enzymes
characteristic of their blood can be found in other bodily
fluids and tissues.
• In the case of a secretor, investigators can conclude the
blood type by examining the saliva, teardrops, skin
tissue, urine, or semen.
• In a rape case, for example, where the perpetrator is a
secretor, potential suspects can be narrowed down
through blood type analysis.

24. General Questions
Five specific questions as
guidelines for determining the
nature of a crime:
1. Is the sample, blood?
2. Is the sample, animal blood?
3. If the sample is animal blood,
from which species did it
come from?
4. If the sample is human blood,
what type is it?
5. Can the sex, age, and race of
the source of blood be
determined?

25. Screening Test (Is it Blood?)
1. Luminol Test
o To reveal these traces with a light-producing chemical reaction
between several chemicals (ie hydrogen peroxide) and hemoglobin,
an oxygen-carrying protein in the blood.Benzidine Test
2. Phenolphthalein( Kastle- Meyer’s) Test
o Phenolphthalein is colourless when it's reduced (has electrons), and
pink when it's oxidized with hemoglobin (no electrons)
3. O-tolidine Test
o a test for the presence of hemoglobin in feces or urine. The O-toluidine
can be in solution, in a tablet or impregnated onto absorbent paper. A
positive test is the development of a green to blue color.
4. Leucomalachite Green Test

26. Luminol Test

27. Phenolphthalein( Kastle-
Meyer’s) Test

28. Screening Test (Human or Animal Blood?)
• Precipitin Test
• Double gel diffusion technique of Ouchterlony(anti-human
hemoglobin tests)
• ABAcard HemaTrace Test

29. ABAcard HemaTrace
• Method of choice today
• An immuno chromographic one-step test for the
detection of human blood
• HemaTrace uses anti-human hemoglobin (Hb)
antibodies to provide a means of detection for the
presence of human blood
• Is coated on test strip and has a detection limit of
0.07 ug Hb

30. Determination of Sex. Race and Age
• Sex Determination
o Presence of Davidson’s body in leukocytes
o Can be identified by as early as 7 weeks into
pregnancy; mother’s blood for Y-chromosome
specific.
o DNA (Positive indicates male fetus)
• Race
o Certain racial genetic markers involving protein
and enzyme tests can help establish race.
• Age Determination
o Fetal Hb indicates fetal blood; also alpha-fetoprotein

31. DNA Test
EDTA is the anticoagulant of choice for blood
collection for DNA extractions
o It inhibits DNase activity and does not introduce
volume changes
o Irrespective of the anticoagulant, the Vacutainer
tube should be inverted several times to mix the
blood
o Sample should be shipped as early as possible
within 24 hrs( delay > 3days degrade DNA )

33. Wet VS. Dry Blood
• Wet blood is more significant than
dried blood because the forensic
scientist can perform more tests in
order to gain insight to the
happenings of the crime. (ie.
alcohol and drug content can be
determined from wet blood only. )
• Blood begins to dry after 3 to 5
minutes of exposure to air.
• As it dries, it changes colour from
deep red to brown and black.
• Blood can be categorized into
pools, drops, smears, or crusts.

34. Nature of Crime
• Murder
o Blood on weapon can be matched against the
blood of the victim
o Blood stains on the clothing's or person of the
accused can be matched with blood of the victim
o Hair roots found on weapon’s can be matched with
blood of victim’s and accused
• Accidental deaths( RTA etc)
o Blood stains on the tyre, radiator grill, and other part
of the offending vehicle may connect victim and it
• Sexual crimes
o Blood stains on thigh and private parts of the victims
• Paternity disputes
o HLA, DNA
• Blood of pregnancy/abortion
o Presence of chorionic gonadotropin ( early stages)
o Heat –stable alkaline phosphatase( late stages)

35. Cause of Death
• Death due to Asphyxia’s :
o Dark fluid blood in heart chambers
• Death due to drowning:
o Alteration in Chloride content( Gettler’s test)
• Death due to poisoning:
o Carbon monoxide poisoning: cherry pink color of
blood
o Cyanide Poisoning: Brick red color of blood
o Heavy metal poisoning (ie. lead): anemia,
basophilic stippled cells

36. Blood Splashes
1930s, Scottish pathologist John Glaister
classified blood splashes into 6 distinct types:
1. Drops on a horizontal surface.
2. Splashes, from blood flying through
the air and hitting a surface at an
angle.
3. Pools around the body, which can
show if it's been dragged.
4. Spurts from a major artery or vein.
5. Smears left by movement of a
bleeding person.
6. Trails, either in form of smears when a
bleeding body is dragged, or in
droplets when it is carried.

37. Categories of Blood Stain
1. Passive (dripping)
2. Transfer (smearing)
3. Projected
o Occur in shootings, trauma from blunt weapons,
hacking, or slashing attacks.

38. Blood Spatter
Passive Spatter Projectile Spatter Contact Spatter
Passive Spatter:
Blood that drips
because of gravity and
as just an after effect
of the violence is
called the passive
spatter.
This can range from
isolated drops of blood
to stagnated pools.
Projectile Spatter:
Blood that drops as a
result of an external
impulse is called
projectile spatter. This
includes blood
projecting from
various wounds as a
direct result of the
violence.
Smearing:
This includes marks
which have been left
as imprints of
something drenched
in blood coming in
contact with a target
area.

40. Projected Blood Stain Analysis
• 2 Important Determinations:
o Direction of splatter
o Angle of impact with surface
• sin = (width drop / length drop)

41. Arterial or Venous Blood
• Arterial blood
o Copious
o Bright red in colour
o Spurting
• Venous blood
o Dark red
o Oozes out gradually

42. Ante mortem / Post mortem Blood
• Ante mortem
o Due to presence of fibrin blood effused
during life can be peeled off in scales upon
drying
• Post mortem
o Blood flowed after death tend to break into
a powder upon drying

44. Precaution
• Wear protective clothing, gloves, masks, and/or eye
protection as the situation warrants
• Photographs should be taken from all angles

45. Liquid / Fresh Stain
• A clean white filter paper or a piece of clean white
cloth; a control filter paper should be also sent if
object is porous, obtain a portion of the unstained
area as well

46. Old and Dried Stain
• Should be carefully scraped if on a immovable
object.
• Scrapings placed in clean containers or envelopes
sealed and labelled.
• On clothes or fibres.... Scrapped off or a fragment
of the material cut, collected in paper bags, sealed
& labelled.
• Dried blood stains on weapons, garments, etc. can
be left intact and entire object submitted.
• Tape lifting bloodstains
o If finger prints present

47. Solvent of Blood
• 10 % solution of potassium cyanide
• 10% solution of glycerin in distilled water (most
common)
• A weak solution of ammonia
• Methods
o Sample can eluted by rubbing the stained area
with cotton swab moistened with distilled water,
the swab is air dried and not heated. Placed in a
sterile swab tube, labeled and sealed
o Arrange and write the swabs and collected
samples in sequence of collection

48. Preservation of Blood
• Sodium fluoride
• Potassium oxalate / lithium or ammonium oxalate,
• EDTA
• Citrate( sodium citrate)
• Sodium Iodo acetate
• 4 degrees Celsius Temperature

49. Conclusion
• Blood is an important evidence in crime scene and
must be carefully detected and collected.
• Blood screening is used generally to screen out the
suspects not involve and to provide a more solid
evidence to determine the criminals.

50. References
• Bureau of Criminal Apprehension. Available at:
https://dps.mn.gov/divisions/bca/bca-divisions/
forensic-science/Pages/forensic-programs-crime-
scene-luminol.aspx
• Science Service Justice.
http://www.nfstc.org/pdi/Subject02/pdi_s02_m02_0
2_b.htm
• UCSB Scienceline. Available at:
http://scienceline.ucsb.edu/getkey.php?key=2777