In what was believed to be the first medical malpractice trial on the United States stemming from a doctor's use of the controversial cancer treatment Laetrile, a federal court jury here yesterday awarded $15,000 damages to the widow of an Alabama man who died after being treated with Laetrile by Rep. Lawrence P. McDonald (D-Ga.).

McDonald, 42, a praticing urologist before his election to Congress in 1974, said he would appeal.

Following an emotional and sometimes tumultuous three-week trial which had both medical and political overtones, the six-member jury ordered McDonald to pay damages only for the "medical and other expenses attendant upon the last illness" of the Laetrile patient.

The jury rejected plaintiffs' request for damages for "pain and suffering" and for possibly shortening the cancer patient's life.

"It didn't do any good, but it didn't cause his death," said juror Chris Boyes, describing the panel's attitude toward Laetrile, an extract of apricot kernels. The verdict, coming in the second day of deliberation, left neither side in the case happy.

The family of John L. Scott, a retired Birmingham, Ala., postal worker, had sued McDonald and Atlanta's Doctors Memorial Hospital for $6 million, claiming malpractice in the treatment of Scott with Laetrile between August 1973 and March 1974, when Scott died of cancer.

McDonald, who worked in an Atlanta urology clinic, has said he had a Laetrile practice on the side in which he treated approximately 200 patients for all forms of cancer.

During the trial, politically conservative and pro-Laetrile groups rallied to the side of McDonald, a member of the National Council of the John Birch Society, who was first elected to Congress in 1974, and who is an emerging national leader of conservative causes.

They included officials of the California-based Committee for Freedom of Choice in Cancer Therapy, the spearhead of the pro-Laetrile movement in the United States. The committee. for which McDonald is listed as "legislative representative," this week began to national campaign to raise funds for the defense of McDonald and other physicians who may be sued for using Laetrile.

Although District Court Judge Richard C. Freeman insisted throughout the case that Laetrile itself was not on trial, testimony repeatedly returned to the value of the alleged cancer treatment. Attorneys for the Scott brought in more than a dozen conventional medical experts from around the country to give emotional denunciations of Leatrile as "worthless" and "quackery."

In closing statements Tuesday, the family's attorneys asked the jury to give a verdict which would serve as a warning to other doctors and hospitals administering Laetrile.

"You must punish them and you must deter them," said L. Burke Lewis, chief attorney for the plantiff. On one occasion during the trial, with McDonald on the witness stand, the chemical name for Laetrile. He court along with a mortar and pestle and dared McDonald to eat the ground up kernels.

McDonald declined, but did offer to take injections of liquid amygdalin, the chemical name for laetrile. He was never asked to actually take the injection.

The behavior of Lewis became an issue in the trial as Judge Freeman repeatedly admonished the attorney to ask fewer question's about Laetrile and more about the Scott case.

Four times, the attorney was held in contempt by Freeman who once ordered Lewis to jail, then said he would sentence Lewis at the end of the trial.

Testimony held, that Scott first learned of Laetrile through his son, a paid organizer for theJohn Birch Society in Alabama.