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88                                                MEDICAL JURISPRUDENCE

menstruation, abortion, parturition or haematemesis, whether it is from an
assailant or a victim, and whether it was shed before or after death. But it
is not helpful in solving these problems. It gives an idea about the size,
thickness and colour of the stain and perhaps the direction from which the
blood came.

It is difficult for a medical man, even of much experience, to offer an
opinion as to the age of blood stains. It is a fact that medical men in India
do sometimes make far too definite statements in this matter. A young in-
experienced doctor is apt to make such a statement under the impression
that the court would think him a fool if he did not give a definite opinion
as regards the age of a stain, but he should remember that it is practically
impossible to say more than that the stains are fresh or not fresh.

The appearances of stains as to whether they are fresh or not depend
on the colour and the nature of the material. Recent stains on a white cloth
are of a brightjred colour which, on exposure to light and air, gradually
changes to reddish-brown in about twenty-four hours, especially in hot
weather, and subsequently changes to dull brown ; this is fairly permanent
but in the course of time it may become Black. 4It is, therefore, evident that
an expression of opinion as to the age of blood from consideration of its
colour is well-nigh impossible. Dry stains have a starchy feel on cloth
composed of a thin fabric, such as cotton, silk or linen.

Stains of recently effused blood on a hard substance, such as stone, iron,
steel or any other metal, have a darX_shining appearance, while dry and old
ones have often a cracked^or^fissured look. Recent stains are also more
soluble in distilled water or normal saline than old ones in which haemoglobin
gradually changes to methsemoglobin and finally to insoluble haematin. Blood
effused during life, when dry, can be peeled off in scales owing to the presence
of fibrin in its coagulum, but it is liable to break up into a powder if shed
after death.

The recently shed arterial blood is bright red in colour, and the venous
blood is dark red, but this difference can hardly be distinguished in a dried
stain. The arterial blood is seen in the form of jets or sprays, which have
an appearance of elongated, pear-shaped marks which may be compared to
' signs of exclamation'. The jets may be projected to a distance of three
to four feet, if effused from small arteries. _The arterial blood is always shed
during life, as blood-pressure in arteries falls to zero after death.

It is not possible to state from the appearance of stains whether they
are of menstrual blood or from any other source. It may, however, be noted
that stains due to menstrual blood and haematemesis are acid in reaction
owing to the presence of vaginal and gastric secretions, but in blood stains
the ordinary method of testing the reaction is hardly applicable. ^B^xarai-
nation under the microscope will determine the nature of the source. ]KTis not
correct to suppose that menstrual blood does not clot; the vaginal mucous
secretion may only delay clotting.

Whether blood stains belong to an assailant or a victim can be determined
only from circumstantial evidence by examining an article of clothing. If
the stains are on the inner side of a garment it is very probable that they
belong to a victim, but, if on the outside, they may belong to an assailant,
thotigh not necessarily so, as the stains would be found on the outside of a
garment worn by a man who received a blow on the head, while standing.
Again, an assailant may not show any stains of blood if he is so standing
as to avoid splashing from the outflow of blood while inflicting an injury.
Besides, he may have changed the clothes or may have washed them, but
blood stains which are faint and invisible by ordinary light after the washing
of the clothes are rendered quite visible when they are exposed to the ultra-
violet rays or when they are photographed with infra-red sensitive plates.