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 New York, spouses seeking a divorce have the option to file on either fault or no-fault grounds. No-fault divorce became available in New York in 2010, allowing a spouse to file for divorce by claiming an irretrievable breakdown of the marriage for at least six months. Prior to this, New York was a fault-based divorce state. However, fault-based grounds are still available and include adultery, cruelty (mental or physical abuse), abandonment for a continuous period of one year or more, imprisonment of a spouse for three or more consecutive years, and living separate and apart pursuant to a separation agreement or decree for at least one year. When it comes to the division of marital property, New York is an equitable distribution state, which means the court divides marital property in a way that is fair, but not necessarily equal. While New York courts primarily focus on equitable distribution without regard to marital fault, they may consider fault under certain egregious circumstances when it would be 'unconscionable' to ignore it. However, such instances are rare, and fault is not typically a major factor in the division of property. Fault may be more relevant in determinations of spousal support and child custody.