Duress has been defined as a "threat of harm made to compel a person to do something against his or her will or judgment;
esp., a wrongful threat made by one person to compel a manifestation of seeming assent by another person to a transaction
without real volition." An example is in Barton v. Armstrong, a decision of the Privy Council. Armstrong threatened to
kill Barton if he did not sign a contract, so the court set the contract aside. An innocent party wishing to set aside a contract
for duress to the person need only to prove that the threat was made and that it was a reason for entry into the contract;
the onus of proof then shifts to the other party to prove that the threat had no effect in causing the party to enter into
the contract. There can also be duress to goods and sometimes, the concept of 'economic duress' is used to vitiate contracts.
Undue influence is an equitable doctrine that involves one person taking advantage of a position of power over another
person. The law presumes that in certain classes of special relationship, such as between parent and child, or solicitor and
client, there will be a special risk of one party unduly influencing their conduct and motives for contracting. As an equitable
doctrine, the court has the discretion to vitiate such a contract. When no special relationship exists, the general rule is
whether there was a relationship of such trust and confidence that it should give rise to such a presumption. See Odorizzi
v. Bloomfield School District.