The Merit Systems Protection Board recently tried to clarify a murky area of federal personnel law by resolving a string of cases that posed the same legal question: When can the government fire an employe because of what he or she did off the job?

The three-member panel unanimously upheld firings in nearly a dozen cases, involving employes who had been convicted of sexual assault on a child, falsifying travel vouchers, rape, hit-and-run driving and assault with a deadly weapon, among other things. But it split sharply over an appeal filed by a Treasury Department employe who was fired in 1981 after he was convicted of drug charges.

In a dissent, Dennis M. Devaney, the board's only Democrat, contended that MSPB Chairman Herbert E. Ellingwood and Maria Lucia Johnson had reversed board precedent and interpreted personnel statutes so strictly that a federal employe convicted of a drug-related crime, even smoking a marijuana cigarette at home, could be fired.

The case has sparked considerable debate among federal personnel attorneys, some of whom contend that it will hold federal employes to a tougher code of conduct in their off-duty hours.

Benjamin F. Harrison, a GS-12 computer programmer, had an unblemished seven-year record as a federal employe when he was convicted in late 1980 of possessing 20 pounds of marijuana with the intent to distribute. Treasury officials immediately moved to fire Harrison, but it took them six months to do it. During that time, Harrison continued to receive the highest job performance rating and was recommended by his supervisors for a promotion.

Under the Civil Service Reform Act of 1979, federal agencies are prohibited from discriminating against an employe for his off-duty conduct unless there is "direct proof" that the conduct had an adverse effect on his job performance.

Former representative Herbert E. Harris (D-Va.), who sponsored the off-duty provision, explained at the time that he wanted "to divorce" an employe's personal problems from his work. In the conference report, the House said in comments to the conferees that it would be improper for an agency to fire a worker solely because of a criminal conviction. A "nexus" -- or connection -- between the crime and the "employe's work or the work of his peers" had to be shown.

Several agencies later complained about the law, saying it was nearly impossible for them to show a direct link between improper conduct off the job and job performance, even in cases where workers were convicted of violent crimes.

In 1981, the board ruled that an agency could fire an employe without direct proof of a nexus under two conditions. The crime had to be so "egregious" that a reasonable person would "presume" that it would have a "substantial adverse impact on the employe's ability to do his job." In addition, there could be no evidence that showed the crime had not had an adverse impact.

Personnel officials applauded the decision, but it soon resulted in several conflicting decisions as federal appellate judges, who hear cases appealed from the board, interpreted "egregious" conduct differently.

By issuing a string of decisions, the Reagan board hoped to provide the guidance the judges needed. In most of the cases, the board ruled against the employe and found that there was a connection between job performance and the crimes, which were felonies in most of the cases.

The Treasury Department had contended that Harrison's conduct also was egregious and that therefore he could be fired. But an MSPB hearing officer rejected that claim, in part because Harrison maintained such a good work record, even after his conviction. The agency appealed the ruling.

In their decision, Ellingwood and Johnson said it was not necessary for the agency to meet the egregious conduct test because there was direct proof of a nexus between the crime and Harrison's job.

Harrison had access to federal checks, they explained, and he had been convicted of a crime that "necessarily required deliberation, concealment and planning for personal gain."

Therefore, "a permissible inference of untrustworthiness may properly be drawn when considering his continued employment . . . . Certainly, the agency was not required to continue placing trust and reliance in Harrison, who voluntarily involved himself in such illegal conduct . . . ," the majority ruled.

In his dissent, Devaney contended that the majority had "equated" Harrison's conviction with a "lack of honesty in federal employment" -- something that Congress had tried to prevent by requiring that an agency prove that the crime had had an adverse impact on job performance.

"This novel legal distillation is proclaimed without citation to precedent or to the record," he complained.

Devaney said that he did not relish defending someone who had been convicted of drug trafficking, but that Harrison had worked for the government for seven years without a problem and that it was unfair to say his bosses did not trust him since he had been recommended for promotion. (Harrison died while the case was under appeal, but his relatives have continued the litigation and asked for any back pay due him.)

"I don't know where the line is drawn now," Devaney said. All drug-related crimes require "concealment, deliberation and planning," he explained, so a "nexus per se" could be claimed in all of them, even instances in which an employe is "arrested at his home for smoking a marijuana cigarette."

Harrison's attorney has 30 days in which to appeal the ruling.