Generally, a divorce can only be "opened" if there was fraud or a failure in one party's financial/property disclosure--but it’s very rare that a divorce is reopened.
In some situations, new evidence, facts, and information can surface after a divorce has been finalized. In these situations, a Motion to Modify may not offer a sufficient remedy. When that happens a Motion to Open is one of the procedural vehicles that can be used so that the court can reconsider any and all questions originally raised and impacted by the introduction of the new information.
Generally speaking, a Motion to Open in Connecticut must be filed with respect to a divorce within (4) four months of the date of judgement. There are further exceptions when a judge finds "good and compelling reason" or the parties mutually agree to waive this requirement. Other exceptions to the (4) month limitation include: Fraud, the Absence of Consent (including Duress), and Mutual Mistake.
Motions to Open based on Fraud represent a rapidly evolving area of family law in Connecticut. Such matters are best handled by an experienced divorce and family law attorney.
A Motion to Open due to Fraud presents a very, very high bar. The Fraud must rise the level that there is a reasonable probability that the result of a new trial would be different. Additionally, there must be no unreasonable delay by the party bringing the motion following the discovery of the fraud. And lastly, there must be clear proof the the Fraud and/or perjury.