How can you sign a will if you are physically unable to sign it?

In other words, how does it work in cases when a person is disabled and can not sign, physically, the will?

If the concrete elements demonstrate that the testator had full mental capacities in the occasion where they expressed the will, it is not relevant that the testator had lost the physical capacity to sign the document.

In Brazil, the capacity can be certified by Notary Public in the occasion of deed of the will, which will avoid future judicial inquiry. However, even if there are inquiries, it must prevail the act from the person which had the mental capacity preserved, regardless any sequels or physical incapacity.

Recently, the justice, in Brazil, decided that a digital signature or even a fingerprint, can confirm the act, if the mental capacity is proved through witnesses and/or other elements.