Hydrostatic Test/Raygat’s Test, Hydrostatic Test

Hydrostatic test/Raygat’s test:

§         It is based on the fact that on breating, the volume of the lungs is increased, which more than compensates the weight of the additional blood, due to which their specific gravity is diminished. The specific gravity of the lungs before respiration varies from 1040 to 1050, and after respiration about 940.

§         A ligature is tied on the bronchi and lungs separated. Each lung individually is placed in water. If they float, each lung is cut into twelve to twenty pleces and placed in water. A small piece of liver may serve as control.

§         If the liver floats, the test is of no value. If these pieces float, they are each squeezed in between thumb and index finger under the surface of water, to see if any bubbles of air escape and if they still persist to float, or they are taken out of water, wrapped in a piece of cloth and squeezed by putting a weight to remove the tidal air.

§         The pieces are again placed in water, and if they continue to float, due to the presence of residual air, in indicates that respiration has taken place. If the pieces sink after pressure, respiration has not taken place.

§         If some pieces float while others sink, it show feeble respiration. A piece of lung is rolled gently between the finger and thumb very near to the ear. A cracking crepitant noise indicates a significant degree of respiratory activity.

§         The hydrostatic test is not of much value, because the lungs of the liveborn who have lived for few days may sink and the lungs of the stillborn may float.

Q.40. What is the fallacies of hydrostatic test?

The test is not absolute proof of live birth for the following reasons-

1. Unexpanded portions of lungs may float in water due to emphysema caused by putrefactive gases and artificial respiration.
2. Unexpanded portions of lungs, on the other hand, may sink in water owing to changes produced by the intra-uterine diseases, such as condolidation, oedema, congenital tumours etc.
3. The child may live for a considerable time after birth without respiration in asphyxia neonatorum.
4. Partial breathing such as ‘vagitus uterinus’ and ‘vagitus vaginalis’ hardly inflates the alveoli of lungs sufficiently to make the hydrostatic test positive.
5. It is more common to find the child taking breath after it’s head is out of the mother’s birth canal which constitutes birth in Bangladesh, but not according to English law.

Nice for viva:

§         Volitional activity: It is a period between the injury & death when he walk, do some works before death. This works are volitional activity. Eg. After shooting himself, a person walk some distance, put/keep the pistol in the drawer & then die.

§         Opinion in case of death due to Hanging: The death in my opinion is asphyxial death leading to respiratory failure caused by hanging which was antemortem & suicidal in nature.

§         Mechanism of drowing: A person does not know swimming or weak goes down the water float (as he is lighter than the liquid displaced by himself) due to alveolar air he will try to respirate ingest H₂O into respiratory tract stimulate the post pharynx cough reflex air is displaced from lung the person is drowned again.

§         A person can be drowned into shallow tank. eg. Ankle level water is enough tin Drunker. Epileptics, Children, Unconscious, Weak & incapacitated.

§         Causes of immediate immersion: (Normal sinking mechanism is not occur)

       1.            If death is due to vagal inhibition.

       2.            If death is due to epileptics.

       3.            Dead body is thrown in water.

       4.            Body is carried along strong tidal current.

§         Causes of non-floatation of body:

1. The body is entangled with substance.
2. Soft tissue is eaten up.
3. Heavy wt. Tight up.
4. Body is tightened to heavy fixed object.

§         Causes of death in drowning:

1. Vagal inhibition.
2. Asphyxia from laryngeal spasm.
3. Haemodilatation (Fresh water drowning)
4. Haemoconcentration (Salt water drowning)

 §         Circumstances of drowining:

1. Accidental
2. Suicidal
3. Homicidal
4. Surreptitious disposal: A person is killed at one place & dispose at other place to hide the crime & to mislead the investigation.

Q.41. When drowning is homicidal?

Ans.

1. Hand & feet tied in a way which cannot be done by the person himself, placed in gunny bag.
2. Injuries are severe enough not be self inflicted & severe to cause death.
3. If ligature is found.
4. If heavy wt. is found attached to the body.
5. If body is found inside gunny bag.

Nice for viva

§         Washerman’s hand: The body was in water for long time. So, hands & feets become white.