In terms of divorce defenses under Mississippi law, "antenuptial knowledge" may simply be defined as a complaining-spouse's (the spouse filing for divorce) pre-marital knowledge of the defendant-spouse's pre-existing bad habits, condition, or other marital impediment that now is alleged to present a cause for divorce. For a defendant-spouse to rely on the defense of antenuptial knowledge, there must be evidence that the complaining-spouse was fully aware of the defendant's alleged pre-marital conduct before entering into the marriage, or evidence showing that the complaining-spouse had such reliable information that a reasonable person would have known about the defendant's particular pre-marital conduct, which is the alleged ground for divorce. See N. SHELTON HAND, MISSISSIPPI DIVORCE, ALIMONY, AND CHILD CUSTODY § 5:13 (2014). Thus, actual or constructive antenuptial knowledge of a defendant-spouse's impediment giving rise to the divorce is sufficient to establish a valid defense against the divorce in Mississippi.
Since 1959, there seems to be no significant case addressing the antenuptial knowledge defense by the Mississippi Supreme Court or Court of Appeals. The most notable case where the Mississippi Supreme Court directly and substantively addressed the antenuptial knowledge defense to divorce was in Kincaid v. Kincaid. In that case, the wife filed for divorce asserting that her husband was a habitual drunkard. Kincaid v. Kincaid, 42 So. 2d 108, 109 (Miss. 1949); see MS § 93-5-1 (5) (2014). Seeking to prevent the divorce, the husband in the case claimed that the wife knew or should have known of his habitual drunkenness before the marriage and therefore should not be able to complain about it now. Accordingly, the Mississippi Supreme Court explained that the crucial issue in the case was whether the husband sufficiently established that the wife knew or had good reason to know of the husband's habitual drunkenness at the time of, or before, the marriage. Id. In assessing Mississippi law, as one commentator has stated, the Kincaid court "suggested that premarital knowledge of  conditions such as habitual drunkenness, drug use, imprisonment or impotency may bar divorce." DEBORAH BELL, BELL ON MISSISSIPPI FAMILY LAW § 4.03 (2d. ed. 2011). Ultimately, the Kincaid court held that there was not sufficient evidence to establish the wife's antenuptial knowledge of the husband's habitual drunkenness in order to bar a divorce because "[a]t the most, she knew only that he was an occasional and moderate social drinker [, not] an habitual drunkard before marriage . . . ." Id. at 109-110.