Most states allow spouses seeking a divorce to allege fault in the breakup of the marriage as a basis for the divorce. Alleging the other spouse’s fault—rather than seeking the divorce on no-fault grounds (irreconcilable differences or incompatibility, making the marriage unsustainable)—is generally a basis for requesting the court make an uneven distribution of the marital or community property in favor of the spouse alleging the other’s spouse’s fault.

In states that allow a spouse to seek a divorce on fault grounds, the grounds that may be alleged vary from state to state, but generally include adultery, cruelty, conviction of a felony, family or domestic violence, abandonment, mental illness, and substance abuse (drugs and alcohol). Spouses may also seek a divorce on no-fault grounds in these states.

In no-fault states, a spouse is not allowed to allege fault as grounds for the divorce, and the court is not allowed to consider fault in dividing the marital or community property—but allegations of fault may be considered for other purposes, such as spousal support and child custody. No-fault states include California, Colorado, Florida, Hawaii, Indiana, Iowa, Kansas, Kentucky, Michigan, Minnesota, Missouri, Montana, Nebraska, Nevada, Oregon, Washington, and Wisconsin. And in some states “incurable insanity” is a no-fault ground for divorce.

The grounds on which a spouse may seek a divorce (fault or no-fault) are usually located in a state’s statutes—often in the family code or domestic relations code.

In Idaho, spouses seeking a divorce have the option to file on either fault or no-fault grounds. No-fault divorce is based on irreconcilable differences, indicating that the marriage is irretrievably broken without assigning blame to either party. However, Idaho also allows for fault-based divorces, where one spouse can allege specific grounds for the divorce that attribute the breakdown of the marriage to the other spouse's actions. The fault grounds recognized in Idaho include adultery, extreme cruelty, willful desertion, willful neglect, habitual intemperance, and conviction of a felony. When fault is alleged and proven, it can influence the court's decisions regarding the division of marital property, potentially leading to an uneven distribution in favor of the non-faulting spouse. Additionally, while fault may not be a primary factor in property division in no-fault states, in Idaho, fault can still be relevant to determinations of spousal support and child custody.