Duress is that which prevents the intent of the testator from being exercised by the use of force or the threat of harm.
It does not depend upon the motive of the wrongdoer, but rather upon the subjective fears of the testator, and is often proven by the doing of a wrongful act of violence and/or the menace or the threat that the act will be repeated.
Duress differs from undue influence in that duress involves more of a threat or performance of a wrongful act that coerced the testator.
The basis for a finding of duress may be due primarily to physical violence that the estate beneficiary had displayed and the possible fear by the decedent that such violence would re-occur if she changed her Will.