Donation Mortis causa is instituted by the DOnor to the donee during his lifetime. It would only have the force and effect upon the demise of the donor.
On normal circumstances, this procedure is instituted by the donor to insure legality that donee or legal heirs will be given their respective properties. The donor should sign the donation mortis causa infront of three (3) witnesses and this is specific "during the signing" otherwise the donation will be rendered defective. WHy is this so, the probate court will ask the witnesses if indeed the donor really signed the donation in his own freewill to protect the donor from coercion and or under duress at the time of his signing.
After signing have it notarized and a copy should be given to the notary public for future reference.