Dying declarations are statements of material facts concerning the cause and circumstances constituting the res gestae of any felony made by the victim voluntarily while not mentally ill and under the fixed and solemn belief that his death is inevitable and near at hand.
In all prosecutions for manslaughter or murder, all dying declarations are always admissible in evidence, if the deceased would have been a competent witness if living.
All such declarations are also admissible in behalf of the defense.
SDCL 23A-22-12