The Indian Succession Act,1925
Section 59. Person capable of making wills
Every person of sound mind not being a minor may dispose of his property by will.
Explanation 1.–A married woman may dispose by will of any property which she could alienate by her own act during her life.
Explanation 2.–Persons who are deaf or dumb or blind are not thereby incapacitated for making a will if they are able to know what they do by it.
Explanation 3.–A person who is ordinarily insane may make a will during interval in which he is of sound mind.
Explanation 4.–No person can make a will while he is in such a state of mind, whether arising from intoxication or from illness or from any other cause, that he does not know what he is doing.
(i) A can perceive what is going on in his immediate neighbourhood, and can answer familiar questions, but has not a competent understanding as to the nature of his property, or the persons who are of kindred to him, or in whose favour it would be proper that he should make his will. A cannot make a valid will.
(ii) A executes an instrument purporting to be his will, but he does not understand the nature of the instrument, nor the effect of its provisions. This instrument is not a valid will.
(iii) A, being very feeble and debilitated, but capable of exercising a judgment as to the proper mode of disposing of his property, makes a will. This is a valid will.