Stephan Schmidheiny, the former Swiss owner of a company producing Eternit fibre cement, and Jean-Louis Marie Ghislain de Cartier de Marchienne, a major Belgian shareholder, are being tried in their absence and face 20 years in prison.
The allegations concern asbestos production at four Italian facilities and involve employees who worked there as well as people who lived nearby.
Schmidheiny and De Cartier are accused of causing an environmental disaster and failing to comply with safety regulations.
Over 6,000 people are seeking damages in the long-running lawsuit in Turin -- the home of auto giant Fiat and Italy's industrial heartland.
"My wife fell ill in January 2007, when she was 47. They removed one of her lungs, but there was nothing to be done. Within 18 months she was gone," Carlo Liedholm, 53, who lived with his wife near one of the factories, told AFP.
"Nothing will bring my wife back. It's unjust that she died like thousands of other people because of delinquent murderers of the worst kind. It's a tragedy that's not talked about anywhere near enough," he said.
"We knew that the material was dangerous from the beginning of the 1960s, it's unbelievable that Eternit was in production until 1986," he said.
Eternit went bankrupt six years before asbestos was banned in Italy in 1992.
Prosecutors have requested that the accused -- Schmidheiny is now 64 years old and De Cartier 89 -- each be sentenced to 20 years in prison.
The crimes carry a maximum 12-year sentence, but prosecutors are seeking a harsher punishment because the fall-out continues to affect victims decades after.
"I have never seen such a tragedy. It affects workers and inhabitants ... it continues to cause deaths and will continue to do so for who knows how long," prosecutor Raffaele Guariniello told the court in his closing speech.
Defence lawyers denied the accused had direct responsibility for the Italian company, and the pair have been absent from court throughout.
The trial, which began in 2009 in Turin after a five-year investigation, is the biggest of its kind against a multinational for asbestos-related deaths, and victims and relatives hope it will set a precedent.
"This trial has international importance for two reasons," said Bruno Pesce, who co-ordinates the association for the families of victims in the industrial towns of Casale Monferrato and Cavagnolo near Turin.
"Firstly, it is the first trial against a multinational of this size, and secondly, in 70 percent of the countries on our planet asbestos unfortunately continues to be mined and used," he said.
"Tens of thousands of people die each year from asbestos-related" illnesses, he said.
The inhalation of asbestos fibres can cause lung inflammation and cancer, and symptoms can take up to 20 years to manifest after exposure.
The defendants' lawyers declined to comment on Monday's expected verdict.
Guido Carlo Alleva, a lawyer for the Swiss billionaire, previously insisted that the trial had failed to prove his client's criminal responsibility.
Pesce said he thought it unlikely that the verdict would close the case.
"I am certain there will be an appeal, because one way or another the decision will not be accepted," he said.
Negotiations between Schmidheiny and local authorities in Casale Monferrato for an out-of-court settlement fell through on February 3rd. The Swiss billionaire had offered the town €18 million ($23 million) to drop the case.
Asbestos, which was banned in Europe in 2005 but is still widely used in the developing world, had been used mainly as building insulation for its sound absorption and resistance to fire, heat and electrical damage.