COURTS ARE TASKED TO DETERMINE NOTHING MORE THAN THE EXTRINSIC VALIDITY OF A WILL IN PROBATE PROCEEDINGS. DUE EXECUTION OF THE WILL OR ITS EXTRINSIC VALIDITY PERTAINS TO WHETHER THE TESTATOR, BEING OF SOUND MIND, FREELY EXECUTED THE WILL IN ACCORDANCE WITH THE FORMALITIES PRESCRIBED BY LAW:

     The burden of proof that the testator was not of sound mind at the time of making his dispositions is on the person who opposes the probate of the will; but if the testator, one month, or less, before making his will was publicly known to be insane, the person who maintains the validity of the will must prove that the testator made it during a lucid interval.  x x x x An essential element of the validity of the Will is the willingness of the testator or testatrix to execute the document that will distribute his/her earthly possessions upon his/her death. (Antonio B. Baltazar et al. vs. Lorenzo Laxa, G.R. No. 174489, April 11, 2012, DEL CASTILLO, J.).