BLOOD STAINS 89
In. this connection it may be mentioned that the accused person may, in
defence, attribute the presence of a few blood stains on his garment to the
stains left by the crushing of bugs, mosquitoes or other blood-sucking insects,
which are not uncommon in India. These stains are small in size and sharply
angular in outline, and may contain eggs and parts of the crushed insect, if
seen under the microscope. The body pulp of the insect does not soak into
the fabric like blood. Stains caused on a garment by droplets of unaltered
blood passed through the anus just after the insect has commenced a feed
are recognizable with the naked eye, although they are quite small. It is
possible that bugs and mosquitoes may suck blood from a person of one blood
group and, on being crushed on a garment of another person of another blood
group, may create a false evidence against the latter of being in possession
of someone else's blood.6
Chemical Examination.—The following chemical tests are applied for
the detection of blood stains : —
1. Guaiacum Test (Van Deen's, Day's or Schonbein's Test).
2. Benzidine Test.
3. Kastle-Meyer Test (Phenophthalein Test) .
4. Leucomalachite Green, Test.
1. Guaiacum Test (Van Deen's, Day's or Schontein's Test).—The usual
procedure for the application of this test is to cut out a small piece of the
stained fabric and to transfer it to a porcelain dish where it is soaked with
a drop or two of fresh tincture of guaiacum. On the addition of a few drops
of old turpentine, ozonic ether or hydrogen peroxide solution, a beautiful blue
colour appears immediately, if the stain is due to blood. If it is not desirable
to cut out the stain, the best way of performing the test is to moisten a piece
of white blotting or filter paper with distilled water and to press it with
gentle rubbing on a small portion of the suspected blood stain. After a little
while, the paper acquires a brownish stain which, if treated with fresh
tincture ,of guaiacum and old turpentine, ozonic ether or hydrogen peroxide
solution, assumes a blue colour.
It is a fairly delicate test revealing the presence of fresh blood in a
solution of 1 : 5,000, but it may not react to very old blood stains. Th^Jtest
also reacts with many other substances, such as saliva, pus, bile, milk, gluten,
gum acacia, oxidizing substances like nitric acid, chromic acid, potassium
permanganate, peroxide of lead and manganese dioxide, chlorine and other
halogens, ferric salts, cupric salts, potassium ferro- and ferri-cyanide, etc.7
Owing to these limitations this test is of doubtful value in medico-legal work.
The guaiacum test was very popular among medical jurists about a
quarter of a century ago, and in fact, it was the only reliable colour test known
to them, but it has now been superseded by more reliable tests.
2. Benzidine Test.—This is a very delicate test, and will detect blood
when present in a dilution of 1 in 300,000 parts. It is now largely used in
medico-legal examination for the detection of blood. The reagents required
for this test are—
(i) Benzidine Solution.—It is prepared by taking 13 cc. of chemically
pure glacial acetic acid in a small conical flask and placing it on a water bath
at 50°C. When warmed (in about 8 to 10 minutes), 1,5 gm. of chemically
pure benzidine (Merck's guaranteed reagent for blood examinatign) are
added and dissolved in glacial acetic acid. The flask is removed from .the
water bath and 57 cc. of double distilled water (distilled in all-glass stills)
6. S. D. S. Greval, Ind. Med. Gaz., June 1947, p. 348.
7. R. W. Webster, Leg. Med. and Toxicol, 1930, p. 167,