The nature of the act of adultery makes it difficult to obtain direct evidence of its commission. Adultery is usually inferred from several circumstances apart from rare cases where spouses are caught in the adulterous act. Adultery may be inferred from surrounding circumstances such as the following:
a. Familiarity: Excess familiarity between the respondent and the co-respondent is not sufficient to establish adultery but it must be shown that there was opportunity to commit adultery. Where a respondent and co-respondent who are fond of each other are seen kissing each other, embracing themselves and spending hours together from which no proper account was given, adultery can be inferred. Akinyemi v. Akinyemi (1963) 1 All NLR 340.
b. Birth of a child: The court will hold the commission of adultery to have occurred when there is birth of a child during the subsistence of a marriage to a respondent, to which the petitioner is not a parent of that child. Pregnancy or the birth of a child for a man married under the Act by a woman other than his legal wife will give rise to the inference that the former has committed adultery. The birth of a child by a wife during the marriage, when the husband had no access constitutes evidence of the commission of adultery. Erhabon v. Erhabon (1997) 6 NWLR (Pt. 510) 667.
c. General cohabitation: Where a party to a marriage is shown to have lived with the co-respondent during the subsistence of marriage to the petitioner, the court will infer the commission of adultery. Evoroja v. Evoroja (1961) WNLR 6.
d. Suspicious circumstances: The court may in certain cases conclude that adultery was committed due to suspicious circumstances. Where a husband visits a wife living apart from him at night and notices the wife’s bedroom in darkness and when the door is opened, the wife and another man are in a state of dishabille, adultery may be inferred from the circumstances. Adeyemi v. Adeyemi (1969) 2 All NLR 181.
e. Conviction of rape: Where there is evidence that a party to a marriage was convicted in Nigeria or elsewhere of rape or any other offence in which sexual intercourse with a person of the opposite sex is an element, it will be evidence that the convicted person committed adultery with the person on whom the rape or other crime was committed. A certificate signed by the registrar or appropriate officer of the court shall be deemed as evidence of the fact and date of conviction. Section 87 (1) (a) Matrimonial Causes Act.
f. Confession and admission: Where a respondent admits to a co-respondent being the mother or father of his or her child, the court will hold the commission of adultery as being established. Alabi v. Alabi (2007) 9 NWLR (Pt. 1039) 297, Megwalu v. Megwalu (1994) 7 NWLR (Pt. 359) 718.
g. Blood test and DNA: In determining whether the applicant is the father or mother of the child, recourse is conferred on the Family Court on the application of a party to any civil proceedings, in which the paternity or maternity of a person falls to be determined, on the use of scientific tests including blood tests and DNA. A court has no power to compel a party to submit to a blood test but it may, draw appropriate conclusion from a refusal.
h. Venereal disease: Where a spouse suffers from a venereal disease which was not contracted from the other spouse, there is a presumption of adultery. Such presumption may be rebutted by proving that the disease was contracted otherwise than by adultery. Butler v. Butler (1917)
i. Frequenting hotels or night clubs with strangers: Frequent visits to nightclubs or hotels with strangers raises a presumption of adultery. Adeyinka v. Ohuruogu (1965) 1 All NLR 210.