What is the dying declaration exception to the hearsay rule?

The dying declaration exception to the hearsay rule has been around for centuries, taking root in the decision of R v. Woodcock[6], a 1789 decision from England: “Now is the general principle on which this species of evidence is admitted is, that they are declarations made in extremity, when the party is at the point of death, and when every hope of this world is gone: when every motive to falsehood is silenced, and the mind is induced by the most powerful considerations to speak the truth; a situation so solemn, and so awful, is considered by the law as creating an obligation equal to that which is imposed by a positive oath administered in a Court of Justice.”