analysis of blood in forensic science

1. FORENSIC CHARACTERIZATION OF BLOOD
Submitted to- Dr. Neelkamal mam
Submitted by- Shabnam
Roll no. - 1303
Class - Msc. forensic 3rd sem.

2. BLOOD
 Blood is specialized body fluid that
transport oxygen and nutrients to
the cells and carries away carbon
dioxide and other waste products.
 Blood has four main components :
plasma, white blood cells, red
blood cells and platelets.
 All blood cells have blood group on
outside the cells.

4. BLOOD COMPOSITION
 Blood having a fluidy portion which called Plasma while
the cellular portion of a blood consist of a Red blood
cells,white blood cells and platelets , all of which
suspended in plasma.
 Plasma (55% in whole blood) constituents such as water
,salt , proteins etc.
 Cellular material ( 45% of whole blood) constituents
RBCs , WBCs , platelets.
 Red blood cells (5 -6 million/ml)– Also known as
erythrocytes . There life span in humans is
approximately 3-5 months . RBCs do not have nuclei
therefore lack nuclear DNA.Erythrocytes consists of
hemoglobin proteins that responsible for transportation
of oxygen.

5. CONT.
 Heme molecule consists of an
organic components known as
protoporphyrin-9 and a ferrous
ion (Fe2+) ion.
 A Heme molecule is known as
ferroprotoporphyrin.The ferrous
ion of heme forms four bonds
with nitrogen of protoporphyrin-
9.

6. CONT.
 White blood cells (5000-10000 /ml) – Also known
as leucocytes, it also plays an important role in
immunity and defense the body against the
infection.
 Leucocytes have nucleus,mitochodria and ameboid
ability.WBCs have a nucleus hence represent the
main source of nuclear DNA from blood.
 WBCs also divided into two components:
1. Granulocytes
2. Agranulocytes

7. CONT.
 Granular leucocytes help to detoxify foreign substances
and respond:
a) Eosinophils
(response to allergic, parasitic infections)
b) Basophils
(responsible for allergic and antigen reponse by
dilation of blood vessels)
c) Neutrophils
(defend against bacterial and fungal infection)
 Agranular leucocytes are phagocytic and produce
antibodies include lymphocytes and monocytes.
 Lymphocytes subtypes further classified:
a) B cells b) T cells.

8. CONT.
 Platelets – Platelets is also called Thrombocytes.
 Platelets derived from multinucleate cells of bone
marrow. Multinucleate cells called megakaryocytes.
 Life span about 5 -9 days.
 Have an ameboid movement.
 Plays an important role in blood clotting.

10. CENTRIFUGED BLOOD
 Plasma proteins –
Albumins (osmotic balance,pH)
Fibrinogen(clotting of blood)
Globulins(defense and lipid trans)
 WBCs or leucocytes + platelets
(present in the form of buffy coat)
 RBCs contains hemoglobin , oxygen
carrying molecules.
1 RBCs = 250 million molecule
of hemoglobin.

11. FORENSIC VALUE OF BLOOD
 Blood has been always considered class evidence
in forensic science.
 Individualization of blood evidence is possible in
near future.( enzyme typing,blood grouping )
 In some cases, forensic serologists were able to
link a single perpetrator to a bloodstains with strong
possible agents.

12. BLOOD EVIDENCE
 Blood is well known and most significant evidence
in criminal justice system.
 Because:
 It can link a victim to a suspect ( via Locard’s
exchange principle ).
 Bloodstain pattern reveals great deal about position
and movement during crime.
 It managed to destroy self-defense arguments of
suspects.
 There are no substitute for it, whether for medical or
forensic purpose.

13. ROLE
 Medical scientists are more interested in white
blood cells (indications for WBC count include
infectious and inflammatory disease, bone marrow
disorders).
 Forensic scientists are more interested in red blood
cells (antigen-antibody based reactions).

14. BLOOD ANALYSIS
 The identification blood is carried out by using
presumptive and confirmatory assays.
 Presumptive assays :- Presumptive assays are
very sensitive , rapid and simple.
 The positive reaction of presumptive assay
indicates the possibility of presence blood in
questions . It is not very specific .
 Hence, its should not be considered as
conclusive result.
 Used as a screening method for narrow down the
identification. It also used as search method to
locate body fluid at crime scene.

15. CONT.
 These assays is based on basic principle of
oxidation –reduction catalyzed by the heme moiety
of hemoglobin . The colorless substance catalyzed
by heme undergo an oxidation reaction causing
either chemiluminescence, fluorescence and
change of color.
 Colorimetric assays- Detect the heme in blood
through color reactions:
 Phenolphthalein assays
 Benzidine assays
 Leucomalachite green (LMG) assays

16. PHENOLPHTHALEIN TEST
 Phenolphthalein is a dye and for blood identification
is also known as Kastle –Meyer test. Kastle publish
the study in 1991 and shows the reaction in which
the phenolphthalein is a colorless compound is
catalyzed by heme with hydrogen peroxide as
oxidant .And resultant pink color appeared under
alkaline condition.

17. PROCEDURE

18. RESULT

19. BENZIDINE TEST
 Benzidine is a dye and also used for presence of
blood detection .In this, the benzidine compound is
catalyzed by heme to produce blue to dark blue
color .Since blue color may eventually turn brown
immediately.
 Benzidine was found to carcinogenic and no use in
forensic testing.
 Orthotolidine is dimethyl derivative of benzidine
which is catalyzed by heme to produce blue color
reaction under acidic conditions.It also considered
as carcinogen based on animal studies and
replaced by tetramethyl-benzidine.
 The TMB continued to be used.

20. BENZIDINE DERIVATIVES
 Benzidine structure -:
 Orthotolidine structure -:
 Tetramethyl-benzidine
structure

21.  Tetramethylbenzidine is catalyzed by heme to
produce green to blue color under acidic
condition.The oxidation reaction takes place.

22. RESULT

23. LEUCOMALACHITE GREEN (LMG)
ASSAY
 The oxidation reaction takes place leucomalachite is
catalyzed by heme group to produce green color.
 The reaction is carried out in acidic condition with
hydrogen peroxidase as oxidant.

24. PROCEDURE

25. RESULT

26. LUMINOL TEST
 Luminol is utilized as chemiluminescent reagent. In
this, the luminol is catalyzed by heme to which
produce light in presence of an oxidant.
 Positive result observe in dark conditions.

27.  Advantage – “Best overall the presumptive test”
 More sensitive and specific in nature.
 DNA preserved.
 Non - toxic nature.
 Resistant (even under 20 layers of plains).
 Disadvantages-
 Examine in dark room condition.
 Short lived.
 No differentiated in human or animal blood.

28. RESULT

30. CONFIRMATORY ASSAYS
 These assays utilized with longer certainity than
presumptive assays.
 It is more specific for identification of blood.
 This assay is performed when sample is identified
as blood.
 Microcrystal assays performed to treat blood stains,
forming crystals of heme molecule.
Takayama crystal assay
Teichmann crystal assay.
 This test cant distinguish between human and
animal blood.

31. TEICHMANN CRYSTAL ASSAY
 It is also known as hematin
crystal assay.
 This method was documented in
1853 of forming crystals of blood
specimens.
 The blood specimen are treated
with glacial acetic acid and salts
and then heated.
 The resultant hematin chloride ,
prismatic brown colored crystal
is formed.
 The hematin assay is more
reliable than hemochromagen
assay for aged blood samples.

32. PROCEDURE

33. RESULT

34. TAKAYAMA CRYSTAL ASSAY
 Also known as hemochromagen crystal assay,
hemochromagen are heme derivatives in which the
ferrous ion of the heme forms two bonds with nitrogenous
bases.
 Takayama crystal assay published in 1912 preferred
methods used by many forensic laboratories.
 A blood stain treated with pyridine and glucose under
alkaline conditions to form crystals of pyridine
ferroprotoporphyrin.

35. PROCEDURE

36. RESULT
 Advantage- More reliable
Good results even with old stains
Heating is not necessary.

37. REFERENCES
 Richard Li Forensic biology book.
 www.wikipedia.com
 https://www.slideshare.net/QuanFuGan/examinatio
n-of-blood.