In PARRICIDE, marriage need NOT be proved by marriage certificate
Parricide is committed when: (1) a person is killed; (2) the deceased is killed by the accused; (3) the deceased is the father, mother, or child, whether legitimate or illegitimate, or a legitimate other ascendant or other descendant, or the legitimate spouse of the accused. The key element in parricide is the relationship of the offender with the victim. In the case of parricide of a spouse, the best proof of the relationship between the accused and the deceased is the marriage certificate. In the absence of a marriage certificate, however, oral evidence of the fact of marriage may be considered by the trial court if such proof is not objected to. [G.R. No. 115686. December 2, 1996]