The final defense of Maryland Gov. Marvin Mandel was a plea to the jury today to consider him an innocent man ruined by a four-year federal investigation that robbed him of his public career, humiliated him and even deprived him of his health and vigor.

At the end of his two-hour closing argument for the governor, Madel's attorney, Arnold M. Weiner, s oftened his voice and told the jury what the proud governor has never said publicly.

"After four years of investigation and two years under indictment, Marvin mandel is a ruined man," Weiner argued. "He has one thing left: He has the presumption of innocence and the benefit of a reasonable doubt."

Following a low-key re ply by chief prosecutor Barnet D. Skolnik, Judge Robert L. Taylor gave the jury its final instructions before it begins deliberations Wednesday at 9 a.m.

The instructions - considered crucial because they define the charges for the jury members - appeared not to surprise or upset lawyers on either side of the case. The failure of a public official to disclose a conflict of interest," Taylor said, is the equivalent of fraud, one of the charges against mandel.

The jurors do not need to be absolutely certain of guilt, the judge said. Guilt can be established even if the government does not prove that "two plus two equals four . . . Intent is a state of mind."

His head bowed slightly, Mandel listened to his attorney describe the consequences the governor suffered that "no one can restore."

"His public career, which was his entire adult life, is finished. Every intimate detail of his personal life has been opened up for the world to see. And I wonder how many of us, the rest of us, could bear that kind of humiliation. Even his health and his strength are gone," WEiner declared.

That statement capped an otherwise forceful rebuttal by Weiner of the prosecution's main contention: that Mandel deliberately manipulated his office to enrich the Marlboro race track, which he alegedly knew was secretly owned by his five codefendants. The same men are named in the endictment as the benefactors who who gave $350,000 worth of favors to the governor.

At one point Weiner attempted to reduced the prosecution's case to one based solely on improper circumstantial evidence that did little more than "put up puffs of smoke."

"It's as if they saw a man standing on a street corner lighting a match, and they screamed 'Arson" and we brought you closer and all you found was that it was a man standing there lighting his pipe." Weiner said, alluding to mandel's trademark: his everpresent pipe.

"I would ask you to consider the presumption of innocence and the burden of proof . . . it means that the government cannot base a case on innuendoes," Weiner said. "The prosecutor has to do more than (require us) . . . to prove to you that there is no fire."

In front of a crowd that spilled into every corner and covered every inch of the steps of the spectator section courtroom; the defense and the prosecution presented their final arguments and ended the entire presentation of the case of the United States v. Marvin mandel et. al.

For the jurors the trial began with opening arguments on june 9 but for the defendants and attorneys the end has come after years of investigation, the November, 1975, indictment and a first trial that was aborted last December after attempts to tamper with the jury.

And although jurors had listened to more than four hours of arguments from Weiner and Skolnik, thet gave permission to judge Taylor to instruct them today in the charges and the law covering the indictment, preparing them for their deliberation on the innocence or guilt of the six defendants.

"We earnestly hope you decide unanimously," Skolnik told the jury as he began his rebuttal to Weiner and the other defense lawyers. "If not . . . the case has to be tried again and that is in the interest of no one."

The prosecution has charged that Mandel received more that $350,000 in jewelry, vacations, clothing, business interests and divorce assistance, from his codefendants, whose own businesses received millions of dollars in state contracts since Mandel took office. Specifically, the government treid to prove that in return. Mandel pushed legislation aiding the racetrack knowing all the while that his friends were the secret owners.

The government testified that he did not know of his friends' interest in the track and that he did not find out until after he took official actions benefiting it.

Weiner ridiculed the prosecution just as prosecutors in their arguments had attacked the defense in sarcastic terms.

"An investigation that went on for more than three years with a team of 10 people," said Weiner, "comes down to a claim in this indictment that in one legislative session (1972) in two matters affecting one racetrack, Marvin Madel is said to have abused his office."

Considering Mandel's eight years in office, he said, the government "came up with very little."

Weiner pointed out the codefendants W. Dale Hess, Harry W. Rodgers III and William A. Rodgers were officers of the Tidewater Insurance Agency. If "Marvin Mandel was to misuse his office in any way, wouldn't that (insuranee) be the area where they had the most to gain?"

Weiner spent only a few minutes of his presentation on the hundreds of thousands of dollars of benefits Mandel received from codefendants including the Rodger brothers, Hess, Irvin Kovens and Ernest N. Cory Jr. Instead, he concentrated on the linchpin of the case: Did Marvin Mandel know his friends owned Marlboro Race Track in 1972 and did he, therefore, "abuse" his office by lobbying legislation to profit the track?

After reminding the jury that 37 witnesses testified abaout Mandel's official actions on a veto override that doubled Marlboro's racing days, Weiner asserted that the "overwhelmingly amount of that evidence overwhelmingly supports the position that the governor and I have been urging upon you," that Mandel took no role in the override and actually disapproved of it.

Weiner attacked one of the prosecution's chief witnesses, Nathan Cohen, a co-owner of Pimlico Race course, who testified that Mandel held a strategy session on racetrack legislation in the Annapolis Hilton hotel with Hess.

"There is a secret in Nathan Cohen's past," Weiner said. "It involves a crime. These people(the prosecutors) know he committed it . . . and for two years now, while he comes in to testify, he has not been prosecuted for that crime."

Weiner did not elaborate except to point out that Cohen had taken the Fifth Amendment when asked about the alleged crime on the stand.

On a second legislative matter that would have benefited Marlboro - Weiner first asserted that as governor of Maryland, Mandel should have been interested in "a major industry of the state - racing."

"When Marvin Mandel lent his support to the 1972 consolidation bill . . . (it) was the very same thing he had done the year before when there were other owners," other than his friends, who bought the track in December, 1971, Weiner said.

"This meeting, with Hess and Cohen at the Hilton is supposed to show, number one, that the governor is down there, sleeves rolled up, killing himself for thi consolidated bill," Weiner said, "and secondly it is supposed to show you circumstantially that the governor knew that Mr. Hess and the Rodgers, knew circumstatially that they owned Marlboro."

But since Mandel, Hess, and Cohen's former lobbyist denied that anything more than a dinner and a short perusal of a delegate list occurred that evening, Weiner told the jury that Cohen's testimony was "nonsense."

Other than two business ventures Weiner claimed were legitimate and one loan, Weiner ignored the benefits to Mandel, the Florida vacations, the wardrobe, diamond jewelry, financial help with his divorce.

After Weiner's defense, Skolnik addressed the jury in an uncharacteristicly quiet and slow delivery.

First, he said, he wanted to rid the jury of the impressions left by the other attorneys that he was a "freight train" or someone capable of convicting a saint, as defense lawyers had said. "I think it is something of a stretch to compare any of the defendants in this case . . . to a saint."

"This case is not about three prosecutors . . . this is not our indictment," Skolnik said. "Some of the defense attorneys . . . called us some names. I hope you will put that aside and not hold it against their clients and certainly not hold it against the prosecutors."

In Taylor's instructions, the judge noted that 20 of the 23 counts in the indictment returned Nov. 25, 1975, charge each of the six men with mail fraud.Judge Taylor said that to return guilty verdicts, the jurors must find that the defendants "used the mails with a conscious attempt to defraud the government." Mail fraud laws were established, the judge said, "to protect the post office from [persons] carrying out schemes, or false and fraudulent pretenses. . . ."

The other three counts to be considered by the jury are anti-racketeering statutes, originally approved by Congress toa fight organized crime, but applied in this case to the governor and his friends.