Arlington prosecutor William S. Burroughs Jr. and his opponent in the June Democratic primary, John W. Purdy, disagreed sharply last night over Burroughs' handling of a controversial 1977 double slaying case.

During a wide-ranging and frequently heated 90-minute debate before 75 members of the Arlington Democratic Committee, Burroughs and County Board member Purdy focused much of their attention on the celebrated murder case, which Burroughs personally prosecuted.

Burroughs vigorously defended his prosecution in the slayings of Arlington real estate agent Alan Foreman and Foreman's fiance. Donna Shoemaker. "I made the best of a bad situation," Burroughs said. But he said he feels he has been unjustly "castigated by the press."

Purdy said. "There is a general feeling frequently expressed to me in the community that this case was not handled well."

Richard Lee Earman, a former real estate salesman, was acquitted of murdering Foreman and Shoemaker but recently pleaded guilty to a charge of conspiring with another man, Joseph N. Martin, to kill the couple.

Earman, who has testified at a court hearing for Martin, that he shot the couple to death after Martin hired him to do so, could be sentenced to as long as 10 years in prison. Martin is awaiting trial on a murder charge.

Burroughs' handling of the case has made him a focus of considerable controversy in Arlington legal and political circles and within the county police department.

Saying he has been the victim of "consistently inaccurate" reporting, Burroughs said, "I'm sick and tired of the case. Every time I turn around it's in the news media."

"At least Lee Earman is going to the penitentiary for 10 years," he said. Defending his plea-bargain agreement with Earman, who could not be retired on a murder charge, Burroughs said, "When you're prosecuting a conspiracy, in the end you have to give somebody a break to get them to talk about the others."

The subject of the murder case was raised during a question period.

Purdy, 48, an attorney in Fairfax, said he did not intend to raise the case as a campaign issue but felt he had to respond to questions about it. "It is my impression," he said, "that the police had the right theory in the beginning and that the main problem with the case was excessive interference by the prosecutor."

Burroughs, 40, conceded that his record as prosecutor is controversial and stressed his decade of experience in Arlington as a defense attorney and assistant prosecutor.

"I have a policy of taking difficult cases," Burroughs told the group. "Up until Lee Earman I never lost a case."

He said, "The conviction rate of my office has steadily increased. Eighty-five percent of those arrested in Arlington for felonies are convicted."

Saying he had practiced law "more than half of my life," Purdy criticized Burroughs' administrative abilities, saying, "There appears to be a lack of direction and guidance in the prosecutor's office." Purdy said if elected in November he would evaluate the nine attorneys in the prosecutor's office.

"I select my people carefully," Burroughs replied, saying he was puzzled by Purdy's criticism. "I supervise them but I don't spoonfeed them."