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 Connecticut (CT), spouses seeking a divorce can file on either fault or no-fault grounds. No-fault divorce is based on the irretrievable breakdown of the marriage, which is similar to the concept of irreconcilable differences. Fault-based divorces, on the other hand, can be sought for several reasons, including but not limited to adultery, cruelty, desertion for at least 12 months, habitual intemperance (substance abuse), and imprisonment. The state's statutes allow the court to consider the causes for the breakdown of the marriage when determining the division of property. While Connecticut is not a strict no-fault state, fault can play a role in the financial aspects of the divorce, such as property distribution and alimony, but the primary focus remains on equitable distribution of marital assets.