There are different grounds for a divorce, separation, and annulment. Some states only have a single ground for divorce- no-fault or irreconcilable differences. Typical grounds for an absolute divorce, are: 

• adultery; 
• desertion (constructive and actual); 
• voluntary separation; 
• criminal conviction of a felony or misdemeanor; 
• insanity. 

In states which grant a limited divorce, you must also have a ground. Typical grounds for a limited divorce are: 

• cruelty (against the child of the complaining party and/or against the complaining party); 
• excessive cruelty; 
• desertion (construction and actual); 
• voluntary separation 

Adultery

Most adultery cases are proven by circumstantial evidence, which means that you have to establish that your spouse had the disposition and opportunity to commit adultery. 

Public displays of affection, such as hand-holding, kissing, and hugging, between the guilty spouse and the paramour are generally sufficient evidence to indicate an adulterous disposition. Opportunity may be proven by showing that your spouse was seen entering the paramour's apartment at 11 P.M. and not coming out until 8 A.M. the following morning and that they were alone.  If you can only prove disposition but not opportunity, the courts may not allow your divorce because the court may reason that it is just mere speculation. The same is true if you only show that there was opportunity, but cannot prove disposition. When you think about it, this seems to make sense. 

Naming the Co-respondent

Sometimes known as a paramour, the co-respondent is the person whom you charge as having committed adultery with your spouse. The co-respondent has the right to hire a lawyer and file an answer to your complaint. Naming co-respondents can get sticky, particularly if your facts are incorrect. You might be damaging the reputation of an innocent person.

The Adulterers

Adulterers are not equal under the blanket of the law. In some states, adultery may impact custody if the adultery is proven to have harmed or impaired the children. Adultery does not necessarily affect alimony awards. It will, however, be a factor for consideration in awarding alimony.

Generally, if you knew your spouse committed adultery but continued to live and cohabit with your spouse, then adultery cannot be used as a ground. Once you resume marital relations, after you learned of the adulterous act, the courts feel that you have forgiven, or "condoned," the act. But, if your spouse starts having affairs again, you can then sue on grounds of adultery. Or, if your spouse has had several affairs and you knew of and condoned only one, you may file on adultery regarding the newly discovered affairs. 

Crimes

If your spouse has been convicted-not simply charged-of a crime, that is a ground for divorce in almost all states. The conviction may be for either a misdemeanor or a felony in any state, but usually the spouse has to serve at least 12 months of a minimum three-year sentence in a penitentiary or penal institution. 

Desertion & Abandonment

For all practical purposes, desertion and abandonment are one and the same.  In  some states, but not all desertion and abandonment are grounds for divorce. There are two elements that have to be present in order to constitute desertion: the willful desire or the intent to desert and the cutting off of the marital relationship. Often  the abandonment has to be: 

• continued for 12 uninterrupted months; 
• must be deliberate and final; 
• beyond any reasonable expectation of reconciliation. 

Actual Desertion

When your spouse packs bags, books, and toothpaste, walks out the door, moves into another apartment, and stays there, he or she is guilty of actual desertion. The spouse voluntarily leaves and has no plans to return except perhaps to pick up a forgotten belonging. 

Constructive Desertion

You also can be deserted even if your spouse does not leave. If your spouse's behavior is so cruel or despicable that you find yourself dialing suicide prevention, you can leave and charge your spouse with constructive desertion. Constructive desertion is basically defined as one person leaving the relationship-not necessarily the home. The following are some cases of marital misconduct that have been applied to constructive desertion: 
 

• Willful refusal of sex, without just cause and nonperformance of other marital duties as to practically destroy the home life. The denial of sex alone does not constitute desertion. The spouse also has to stop carrying out the mutual responsibilities of the marital relationship. 
• Conduct that endangers a spouse's life, safety, health, and even self-respect (although an isolated assault or two will not necessarily constitute cruelty unless the act was particularly severe and atrocious). 
• One spouse's failure to move if, for example, the other gets a job transfer. The exception is if one spouse's choice of domicile is unsafe or unsuitable for the other

If the Deserter Returns

Your spouse has left you, spent six months chasing butterflies, and suddenly wakes up one morning and decides that you are the one after all. In good faith, your spouse shows up at your doorstep and begs you to forgive and forget. In many states, if you say yes, then all is well. But if you say no and refuse to even see or listen to your spouse, then, strange but true, your spouse could sue you for desertion. The waiting period would start all over again beginning with the time of your refusal. Keep in mind that "good faith" is the key. If, for example, your husband deserted you and then tried to return only after realizing what the high costs of his alimony and legal fees would be, his desire to return would not necessarily be considered "good faith".

Insanity

Your spouse must be judged permanently and incurably insane and be confined in an institution or a hospital for a minimum of three years before filing. To prove insanity, two or more psychiatrists are needed to testify that your spouse is incurable and that there is no hope of recovery. The court will appoint an attorney to act in the defense of your spouse whom you purport to be insane. These costs are usually borne by you.

Voluntary Separation

In some states a "no fault" divorce is known as a divorce based on voluntary separation. It usually means that you and your spouse have separated after mutually and voluntarily agreeing that you no longer wish to live together as husband and wife and that there is no hope for a reconciliation. Your spouse cannot threaten or blackmail you into leaving; you separate because you both want to. To get a divorce on this ground you have to be separated for a period of time, often six months or one year, and there is no hope of reconciliation. Remember though, if this is not a mutual and voluntary situation you will have to use another ground to get a divorce.