A federal prosecutor has urged a judge in West Virginia to sentence Donald L. Blankenship, who was chief executive of Company when 29 workers were killed in a mine explosion, to the maximum of a year in jail for conspiring to violate safety standards.

Lawyers for Mr. Blankenship, whom a jury convicted of a misdemeanor charge in December, asked Judge Irene C. Berger of Federal District Court in Charleston to impose a far less severe punishment of a fine and probation.

Mr. Blankenship was not tried on any charges that accused him of direct responsibility for the 2010 deaths at Upper Big Branch mine, which investigators said exploded because of improper ventilation that allowed gases to accumulate. Yet to many critics, Mr. Blankenship’s conviction offers the greatest opportunity for justice after the accident, the deadliest in American mining in four decades.

Judge Berger has scheduled sentencing for April 6, and the memos that lawyers submitted late Monday are expected to shape her decision. Although the Justice Department said that federal guidelines suggested a prison term of 15 to 21 months, the law under which Mr. Blankenship was convicted does not allow Judge Berger to sentence him to more than a year.

“Given the magnitude of defendant’s crime, a sentence shorter than the maximum could only be interpreted as a declaration that mine safety laws are not to be taken seriously,” Steven R. Ruby, an assistant United States attorney, wrote in his sentencing recommendation. He said existing law “offers no adequate punishment” for Mr. Blankenship’s conduct.

During the trial, prosecutors argued that Mr. Blankenship’s seemingly unwavering focus on Massey’s financial performance stimulated a corporate culture in which safety was less a priority than profits. Mr. Blankenship’s leadership style and demands, they said, effectively encouraged lower-ranking employees to cut corners and accept breaches of safety rules.

On Monday, Mr. Ruby said that Mr. Blankenship had “made a conscious, coldblooded decision to gamble with the lives of the men and women who worked for him.” The prosecutor asked, “Which is worse: a poor, uneducated young man who sells drugs because he sees no other opportunity, or a multimillionaire executive, at the pinnacle of his power, who decides to subject his workers to a daily game of Russian roulette?”

Defense lawyers said at trial that Mr. Blankenship had been committed to safety and argued that his demands for greater results hardly amounted to criminal behavior. On Monday, they repeated many of those assertions in their filing, which included more than 100 letters of support for Mr. Blankenship.

“The court cannot and should not conclude that the jury accepted the government’s broad arguments about the nature of the offense and Mr. Blankenship’s role in it,” they wrote.

Mr. Blankenship, who intends to appeal his conviction, was acquitted of three felony charges that together carried the possibility of 30 years in prison. Although Mr. Blankenship’s lawyers did not call any witnesses, they used an aggressive cross-examination strategy to undercut crucial components of the government’s case and told jurors that safety violations in an operation as sprawling as Massey’s were inevitable.

“The fact that other mines received more violations than U.B.B. is not an argument that violations should be excused,” the defense wrote, using an acronym for the Upper Big Branch mine. “However, it rebuts and mitigates the government’s version of the offense — that the number of regulatory citations itself proved widespread lawlessness and a conspiracy of great breadth — and the government’s unsubstantiated theories that less production and more miners would have reduced safety violations.”

The lawyers said Mr. Blankenship set high standards. But they also labored to portray him as committed to safety and to the well-being of West Virginia. “The defense never contested that Don Blankenship could be blunt and a hard taskmaster,” they wrote, “but the truth is that he cares deeply about his family, his community, and the people who worked for him.”

Judge Berger, whose father was a coal miner, has the authority to fine Mr. Blankenship up to $250,000. She may also order restitution, but that sum will probably not be set next week.