For lawyers preparing to sue over Sunday’s deadly New York commuter rail accident, their success in court may depend largely on two factors: whether human error caused the derailment, and whether state or federal law governs railroad safety in the case.

Tens or even hundreds of millions of dollars could be at stake, based on previous cases. In 2009 a Cook County, Ill., jury awarded more than $29.5 million to a Chicago woman injured in a 2005 commuter train derailment.

The investigation into the Metro-North derailment in the Bronx, which killed four and critically injured 11, has centered on the actions of the train’s engineer, William Rockefeller. He told investigators that he lost focus right before the crash, his labor union leader told Reuters.

Investigators have said the seven-car train was traveling at 82 mph (132 kph)—nearly three times the speed limit for the curved section of track where it crashed.

A lawyer for Rockefeller was not immediately available for comment, and the National Transportation Safety Board has said it has not reached a conclusion into the accident’s cause and would continue its work for weeks, if not months.

Authorities have not found any mechanical problems with the train so far, but a safety system designed to keep an engineer alert was not installed in the car from which Rockefeller was controlling the train, a source familiar with the railroad’s operation told Reuters.

If government investigators determine human error caused the derailment, the agency operating the train could be held liable for the negligence of its employees under a common-law doctrine known as “vicarious liability.”

That doctrine could apply, experts say, even if the Metropolitan Transportation Authority, the parent of Metro-North, can say it had no reason to question the engineer’s competence.

“The case will turn on his conduct, not on the conduct of the MTA,” UCLA law professor Richard Abel said.

If the accident is deemed to have been caused by a mechanical failure, liability could be spread among several possible defendants, including manufacturers of any parts found to have failed and various contractors.

No lawsuits have yet been filed in the wake of the crash, but New York plaintiffs’ attorney Michael Lamonsoff told Reuters on Wednesday he had notified Metro-North that he planned to file a negligence suit on behalf of two injured passengers.

Another lawyer, Joel Faxon of New Haven, Conn., said he had consulted with two families about potential claims. The MTA “owns the crash” if there was personnel error, he said.

A spokesman for the MTA declined to comment about the agency’s potential liability.

Metro-North carries $10 million in liability insurance coverage, and the MTA has an additional $50 million through a subsidiary, an MTA official said. The agency also has $350 million in coverage through commercial markets, the official said.

Federal or State Law?

But there is a way for Metro-North to avoid liability—by arguing that federal law, not state law, governs the case.

Defendants can argue that claims typically brought under state law, including negligence, are in fact barred if the conduct at issue is governed by federal laws and regulations.

The doctrine is known as federal pre-emption, and a number of federal statutes address railroad safety and maintenance issues.

If a defendant prevails on the pre-emption issue, it can avoid liability if it can show it complied with federal requirements.

The challenge for the plaintiffs in the New York case is to plead claims that avoid citing conduct covered in relevant federal laws and regulations, said Mike Danko, a California plaintiffs’ attorney.

“That’s where the fight is going to be,” he said.

Metro-North, in fact, raised that argument in lawsuits filed earlier this year by people injured in a May collision of two of its trains in Connecticut. Those lawsuits are still in their early stages, and the pre-emption issue has not been resolved.

Even if it loses on all those issues, Metro-North is likely to argue that as a public entity, it is immune from punitive damages. In civil litigation, judges or juries often award damages to the winning plaintiffs both to compensate them for their injuries and to punish the defendant. But government agencies are often shielded from punitive damages.

Metro-North has also raised that defense in the litigation stemming from the May accident.

If the railway is sued and loses, federal law allows awards of up to $200 million in total to rail passengers for all claims arising from a single incident.

(Reporting by Andrew Longstreth; Editing by Eric Effron, Peter Henderson and Peter Cooney)