What is collusion as a defense?

Collusion is the classic defense, so much so that at one time courts required the parties to certify that they had not acted collusively. In the old fault-only days, couples who wanted a divorce agreed, one with the other, to say that one of them had committed a fault that would give rise to divorce. This usually meant adultery, and this gave rise to the so-called hotel divorce. Essentially the couple tried to defraud the court, and before the case was over both of them perjured themselves.

The trouble happened when before the divorce one spouse wanted to back out of the agreement. Then he or she would claim collusion, and use it as a defense. The movie Gay Divorcee starring Fred Astaire and Ginger Rogers humorously depicts a divorce and collusion.

The same basic routine could be applied using other fault grounds --cruelty, desertion, drunkenness.