A court cannot raise defences such as condonation and waiver mero motu when these were not pleaded or canvassed at trial, as this constitutes deciding a different case and violates the parties' rights. When applying section 9(1) of the Divorce Act, courts must follow a two-step approach: (1) establish the factual basis regarding duration of marriage, circumstances of breakdown, and substantial misconduct; (2) make a value judgment on whether one party would be unduly benefitted without a forfeiture order. Substantial misconduct under section 9(1) includes not only conduct causing marriage breakdown but also abuse and misappropriation of joint estate assets for the benefit of third parties. Spouses married in community of property hold undivided shares in the joint estate and one party cannot control and abuse joint assets as if having marital power. Where one spouse conducts a prolonged, public extramarital affair, establishes businesses with the paramour using joint estate assets, fails to contribute proportionately to household expenses and children's needs, and substantially erodes the joint estate, while the other spouse makes substantial direct financial contributions, the unfaithful spouse would be unduly benefitted without a forfeiture order and should forfeit their share in the other spouse's pension benefits.