That outcome for a derivative suit brought by a shareholder on behalf of a corporation against a third party would be a change, since historically such suits have not resulted in huge payouts and generally have led to agreements for remedial measures and payment of attorney fees, he explained.

"The question of whether there ultimately will be a cash payout--there was a time when I would have said that's not very likely simply because derivatives lawsuits really never resulted in huge payouts," Mr. LaCroix said.

But more recently, he said significant payouts from derivative suits were seen. He pointed to a settlement in 2008 in which former AIG executives agreed to pay $115 million to shareholders, and a $118 million settlement of a derivative suit in 2009 involving chip maker Broadcom as examples.

"There's at least recent historical precedent to suggest a possibility that there could be a large cash payout," Mr. LaCroix said.

Whether there is a cash payout, he explained, may depend on the availability of directors and officers insurance for the executives named in the BP suit, as well as the ultimate objective of the plaintiffs and how the case fares as it proceeds.

The complaint filed on May 7, in U.S. District Court in New Orleans, alleges that BP has a history of "ignoring crucial safety issues related to the operation of offshore submersible rigs" and that executives continued to ignore safety issues after settling a previous shareholder derivative proceeding in 2006.

The complaint mentions a 2005 explosion at a BP refinery in Texas City, Texas in which investigators "determined that BP had ignored its own protocols on operating the tower," and a 2006 incident where BP had to shut down its Prudhoe Bay oilfield in Alaska after oil leaked from a corroded pipeline.

After those two incidents, the complaint states, BP continued to disregard risks.

The suit names as defendants Anthony Hayward, chief executive officer and board member of BP, as well as other directors and officers, and companies that own or have done work on the Deepwater Horizon rig such as Transocean Ltd., Cameron International Corporation, and Halliburton Energy Services, Inc.

Mr. LaCroix said he expects to see additional law firms file similar derivative complaints against BP's executives on behalf of shareholders until the courts can determine a lead law firm. He said a number of lawsuits were filed in the previous 2006 Prudhoe Bay spill.

But speaking to the potential for widespread D&O suits, he said the number of potential targets is limited to BP and a few other vendor and service companies involved in operating and working on the rig.

Howard Mills, chief insurance advisor at Deloitte, said D&O action in oil spills such as this one could be driven by the extent of the damage that ultimately occurs.

He also said if a company has a history of regulatory problems or violations, it could call risk management procedures into question, potentially putting directors and officers on the spot for how risk factors were addressed.

Mr. LaCroix said a broader issue could be whether derivative suits will become more common in future environmental events.