Italian defence group Leonardo's chief executive, Mauro Moretti, was sentenced by a judge to seven years in prison on Tuesday after being held responsible for one of the country's worst train accidents as the former head of the national rail company.
Shares in state-controlled Leonardo were down 3.4 percent at 11.79 euros by 1608 GMT, their lowest level in more than two months.
In June 2009 a freight train hauling liquefied gas derailed, partly overturned and exploded in the Tuscan seaside town of Viareggio, with the subsequent fire and collapse of a building killing 32 people.
Prosecutors in September had asked for Moretti, who led rail group Ferrovie dello Stato from September 2006 until April 2014, to be given a 16-year prison sentence under charges of causing the disaster and consequent deaths.
Under Italian law the decision taken by the court of first instance can be appealed against twice before the ruling is final and the jail sentence has to be served.
No one was immediately available for comment at Leonardo, the Finmeccanica group which was renamed by Moretti last year in reference to Leonardo da Vinci.
Since his appointment by former prime minister Matteo Renzi in 2014 Moretti has overhauled Leonardo's business, cutting costs and focusing on aerospace and defence while shedding non-core assets.
His first term of office at Leonardo comes up for review in April with the government due to make a fresh round of nominations for the top jobs at state-controlled companies, which also include oil company Eni and energy utility Enel.