CNBC: How Safe is a Prenup?:

Prenups are supposed to be the ultimate divorce insurance for the wealthy. Yet like insurance, prenuptial agreements are often challenged when there’s a claim. …

The main reason prenups are so rock solid is the Uniform Prenuptial Agreement Act, which was adopted by the majority of states and makes it very difficult to toss out a prenup. The law sets out basic guidelines for drawing prenups and strengthens their enforceability, attorneys said.

Yet there are a few conditions under which prenups may be tossed out. Attorneys said the most common challenge is fraud, where a spouse undervalues or hides assets. ..

Another popular challenge is the “coercion or duress” argument. This is Anne Griffin’s main argument. She said that after she expressed unwillingness to sign the prenup, they had an argument and Ken Griffin became “so angry, violent and intimidating that he destroyed a piece of furniture in their home.” ….

“If the wealthier party wanted it to be fair, they wouldn’t enter into a prenup,” he said. “Prenuptial agreements necessarily deal with degrees of unfairness. They give leverage to one side.”

That doesn’t mean that less wealthy spouses can’t get more than the prenup offers. In the recent divorce of Wendi and Rupert Murdoch, for instance, Wendi Murdoch negotiated a larger settlement during negotiations involving their assets and children. The Griffin divorce also involves the custody of their children.

“The prenup is just another hurdle for one side to overcome,” Auerbach said.