In a rare prosecution of a mining executive for safety violations, former Massey Energy chief executive Don Blankenship was convicted by a federal jury on one of the three counts brought against him in relation to the 2010 Upper Big Branch mine collapse in West Virginia that killed 29 people.

An investigation of the event found a plethora of warning signs before the accident, including sparking machinery and a buildup of toxic gases. The jury in Charleston, West Virginia, found Blankenship guilty of conspiracy to violate mine safety regulations, which is a misdemeanor, but acquitted him on the more serious counts of deceiving investors and regulators.

His lawyers have reportedly said they would appeal the verdict, which could come with up to a year in prison. Massey Energy’s parent company has already paid $209 million to victims of the disaster, which came after years of fines paid, it seemed, as if they were simply a cost of doing business.

Although it was not everything prosecutors were hoping for, the conviction is more than what government lawyers have managed to achieve in other cases involving mining fatalities. Few chief executives have been hit with criminal charges for accidents in their facilities. Many – like another West Virginia coal magnate, Jim Justice – have even avoided paying much in the way of fines for hundreds of safety violations uncovered by inspectors.

“The fact is that we’ve been mining in this country since 1880 and this is the first time that this has happened,” says former federal mine safety chief Davitt McAteer, who conducted the investigation into the mine collapse. “So I think the consequences will send ripple effects through the industry, and not just mining.”

So what took so long? McAteer suggests that the declining influence of the coal industry made it easier for prosecutors to go after executives. “If you had asked me the question could this have happened 15 years ago, the answer is no,” McAteer said. “You wouldn’t have had the willingness of the U.S. attorney to accept that coal industry persons could be responsible. When coal was king, this could not have happened.”