1.  Generally

Statements made by a person under the sense of their own imminent death which relate to the circumstances of their impending death are admitted under the "dying declaration" exception to the hearsay rule.{footnote}FRE 804(b) (2).
Cal. Evid. Code § 1242. 
Check Shepard v. United States, 290 U.S. 96 (1933) (declarant must have abandoned all hope of recovery and believed death to be immediately imminent); Soles v. State, 119 So. 791 (Fla. 1929).
{/footnote}  Fed. R. Evid. 804(b)(2) states "[i]n a prosecution for homicide or in a civil action or proceeding, a statement made by a declarant while believing that his death was imminent, concerning the cause or circumstances of what he believed to be his impending death" may be admissible as an exception to the hearsay rule.{footnote}Fed. R. Evid. 804(b)(2).{/footnote}  Under the federal rules and in some states, the exception applies to all civil cases and to criminal homicide cases.{footnote}FRE 804(b)(2)
Accord Ariz. R. Evid. 804(b)(2); Conn. R. Evid. 804(b)(2); Dela. R. Evid. 804(b)(2); Idaho R. Evid. 804(b)(2); Kan. Civ. Proc. Code Ann. ? 60-460(e) (Vernon 1994); Md. R. Evid. 804(b)(2); Mass. Ann. Laws ch. 233, § 65 (Law. Co-op. 1986); Mich. R. Evid. 804(b)(2); Miss. R. Evid. 804(b)(2); N.H. R. Evid. (804(b)(2); N.M. R. EVID. 804(b)(2); Ohio R. Evid. 804(B)(2);  Okla. Stat.tit. 12, § 2804(B)(2)(1993); R.I. R. Evid. 804(b)(2); S.C.R. Evid. 804(b)(2); S.D. Codified Laws Ann. § 23A-22-12 (1988),  § 19-16-31 (1995);  Vt. R. Evid. 804(b)(2); Wash. R. Evid. 804(b)(2); W. Va. R. Evid. 804(b)(2); Wyo. R. Evid. 804(b)(2); Commonwealth v. Sowell, 22 Mass. App. Ct. 959, 494 N.E.2d 1359 (1986).
Cummings v. Illinois Central R.R., 260 S.W.2d 111 (Mo. 1954); Noe v. Talley, 38 Tenn. App. 342, 274 S.W.2d 367 (1954).{/footnote}  Most states, however, limit the exception to criminal homicide cases,{footnote}Ga. Code Ann. § 24-3-6 (Michie 1995); Nev. Rev. Stat. Ann. § 51.335 (Michie 1986); O’Cain v. State, 586 So. 2d 34 (Ala. Crim. App. 1991); Burton v. State, 39 Ala. App. 332, 101 So. 2d 564 (1957);  Marshall v. C. GERR Co., 48 Ill. 475 (1868); People v. Walker, 262 Ill. App. 3d 796, 635 N.E.2d 684 (1994); State v. Hodge, 655 S.W.2d 738 (Mo. Ct. App. 1983); Cummings v. Illinois Cent. R.R., 364 Mo. 868, 269 S.W.2d 111 (1954) (en banc), cert. denied, 361 U.S. 964 (1960); State v. Little, 83 Misc. 2d 321, 371 N.Y.S.2d 726 (1975); Commonwealth v. Douglas, 461 Pa. 749, 337 A.2d 860 (1975); Commonwealth v. Brown, 388 Pa. 613, 131 A.2d 367 (1957); Bowling v. Commonwealth, 12 Va. App. 166, 403 S.E.2d 375 (1991); Annot., 47 ALR 2d 526.{/footnote} while a minority apply this exception in all civil and criminal cases.{footnote}Alaska R. Evid. 804(b)(2); Ark. R. Evid. 804(b)(2); Cal. Evid. Code § 1242 (West 1995) (Law Revision Commission comment); Colo. Rev. Stat. § 13-25-119 (1989); Del. R. Evid. 804(b)(2); Fla. Stat. ch. 90.804(b)(2) (1979) (Law Revision Council Note); Haw. R. Evid. 804(b)(2) (Commentary); Ind. R. Evid. 804(b)(2); Iowa R. Evid. 804(b)(2) (Committee Comment); Ky. R. Evid. 804(b)(2);  La. Code Evid. Ann. art 804(B)(2) (West 1995) (Comments to Exception (B)(2)); Me. R. Evid. 804(b)(2); Minn. R. Evid. 804(b)(2) (Committee Comment); Neb. Rev. Stat. § 27-804(2)(b)  (1989); N.C. R. Evid. 804(b)(2) (Commentary); N.D. R. Evid. 804(b)(2) (Explanatory Note); Or. R. Evid. 804(3)(b) (Conference Committee Commentary); Tex. R. Civ. Evid 804(b)(2); Tex. R. Crim. Evid. 804(b)(2); Utah R. Evid. 804(b)(2) (Advisory Committee Note); Wis. Stat. § 908.045(3) (1993) (Judicial Council Committee’s Note).

{/footnote}  New Jersey applies the exception to any criminal case but not to civil cases.{footnote}N.J. R. Evid. 804(b)(2).{/footnote}

The declarant must have been competent at the time of making the statement.  See COMPETENCE.{footnote}  86 ALR 2D 905 .  {/footnote}  The declarant need not have been religious, although if the declarant was not religious, this fact may be considered as to the weight to be given the evidence.  [excluded under FRE?]  See RELIGIOUS BELIEF.  Statements of opinion are not admissible under this exception.{footnote}Shepard v. United States, 290 U.S. 96 (1933); Miller v. Goodwin & Beevers, 439 S.W.2d 308 (Ark. 1969).{/footnote}

Under FRE 804(b)(2), the declarant need not have actually died, so long as he or she is unavailable to testify.{footnote}  See Note to FRE 804(b)(2).{/footnote}  See UNAVAILABILITY.  Most states, on the other hand, apply the "dying declaration" exception only where the declarant has died.  The death need not have been immediately after the declaration [same cause?].  In some states, the jury has a role in deciding whether a statement offered as a dying declaration was made in contemplation of impending death.{footnote}  State v. Proctor, 269 S.W.2d 624 (Mo. 1954); State v. Garver, 225 P.2d 771 (Or.1950).
{/footnote}

2.  Confrontation Clause

Admission of a dying declaration under this hearsay exception has been held not to violate a criminal defendant’s right to confrontation.{footnote}Kirby v. United States, 174 U.S. 47, 43 L.Ed. 890, 19 S.Ct. 574 (1899); Robertson v. Baldwin, 165 U.S. 275, 282 (1897) (admission of dying declarations and depositions of witnesses who have died since the first trial allowed under the sixth amendment).{/footnote}

Bibliography

Rick A. Howard, The Dying Declaration: Return to its Original Application, 19 Am. J. of Trial Advocacy 481 (1995).
Michael H. Graham, Federal Practice and Procedure 6794 (Interim ed. 1992)
Graham C. Lilly, An Introduction to the Law of Evidence § 7.24 (2d ed. 1987)
Charles R. Nesson & Yochae Benkler, Constitutional Hearsay: Requiring Foundational Testing and Corroboration Under the Confrontation Clause, 81 Va. L. Rev. 149 (1995)
Charles W. Quick, Some Reflections on Dying Declarations, 6 How. L.J. 109 (1960).