What is undue influence?

The concept of undue influence that vitiates a contract is discussed in Article 1337 of the Civil Code, to wit:
ART. 1337. There is undue influence when a person takes improper advantage of his power over the will of another, depriving the latter of a reasonable freedom of choice. The following circumstances shall be considered: the confidential, family, spiritual and other relations between the parties, or the fact that the person alleged to have been unduly influenced was suffering from mental weakness, or was ignorant or in financial distress. (n) [Emphasis supplied]
For undue influence to vitiate the contract, the following requisites must occur:

a) there is an improper advantage;

b) power over the will of another; and

c) deprivation of the latter’s will of a reasonable freedom of choice.

In Coso v. Fernandez,[1] the Supreme Court held that the rule as to what constitutes undue influence has been variously stated but the substance of the different statements is that, to be sufficient, the influence must be of a kind that so overpowers and subjugates the mind of a party as to destroy his free agency and make him express the will of another, rather than his own.

Undue influence is not to be inferred alone from age, sickness, or debility of body, if sufficient intelligence remains.[2] The influence must be undue or improper[3] to avoid a contract. Mere general or reasonable influence is not sufficient. If gained by kindness and affection or argument and persuasion, the influence will not vitiate consent.[4][5][6]

[1] Coso vs. Fernandez-Deza, 42 Phil. 596 (1921).

[2] Loyola vs. Court of Appeals, 326 SCRA 285 (2000).

[3] Article 1337, Civil Code.

[4] Supra note 1.

[5] Martinez vs. Hongkong & Shanghai Bank, 15 Phil. 252 (1910).

[6] De Leon. (2014). Civil Code.