Not all states offer a choice between fault and no-fault grounds when you file for divorce. Some, such as California, don't recognize any fault grounds. All states do offer a no-fault divorce, however. A few pros and cons exist as to which is most beneficial to use, depending on your personal circumstances.
No-Fault Means the Divorce Is Nobody's Fault
Filing on fault grounds requires that you charge your spouse with some type of wrongdoing that caused your marriage to end. For example, perhaps he committed adultery or treated you cruelly. Abandonment and desertion are also usually grounds in states that recognize fault-based divorce, as is the conviction of a serious crime. If you elect to file on no-fault grounds instead, you can simply tell the court that your marriage has failed -- and it's not necessarily anyone's fault. This no-fault ground is generally known as irreconcilable differences or irrevocable breakdown of the marriage. In some states, such as Maryland and North Carolina, the no-fault ground is marital separation.
In some states, such as Illinois, filing for divorce on no-fault grounds requires both irreconcilable differences and a period of separation. In North Carolina and Maryland, you must be separated for at least a year before you can file. Citing fault grounds in your petition usually allows you to file for divorce right away – there's no waiting or separation period.
Burden of Proof
The court won't grant you a divorce if you can't prove your grounds, particularly if your spouse contests them. With no-fault grounds such as irreconcilable differences, the fact that you want a divorce is usually a pretty good indication that your marriage isn't working out. If you choose fault-based grounds, however, the challenge of proving them might be difficult. For example, if you file on grounds of adultery, you must usually establish that your spouse both had the opportunity and the inclination to stray, even if he comes right out and admits that he had an affair. Your spouse can raise defenses to your allegations or file a counterclaim alleging you did something wrong as well. In this case, the court might grant the divorce to the party who was the least at fault.
Effect of Fault at Trial
Assuming you're successful at proving fault, the next issue is how it might affect the terms of your divorce. Generally, marital misconduct does not affect custody issues, unless the misbehavior has a direct effect on your children. However, it may present a bar to alimony; in some states, do not award support to a spouse who committed adultery. Marital fault can also affect property distribution. In some states, this is true even if you file on no-fault grounds, if you can prove that your spouse wasted marital assets in the course of committing misconduct. For example, perhaps he spent a great deal of money on someone with whom he was having an affair. In states that don't recognize fault grounds, marital misconduct rarely has an effect on any aspect of divorce, at least if your spouse didn't dissipate marital assets.