A U.S. District Court jury here began deliberations today to determine whether two Filipino nurses are guilty or innocent of poisoning and murdering their patients at a Veterans' Administration hospital in 1975.

One defense lawyer said waiting for the decision will be "scary as hell." Otherwise, the defense had no comment.

Federal prosecutor Richard Yanko expressed confidence that the jury would convict the former intensive care nurses after three or four days of secret deliberations.

The nurses, Filipina Narciso, 31, and Leonora Perez, whose 33d birthday is today, are accused of using the paralyzing drug Pavulon to poison seven of their patients at the VA hospital in Ann Arbor, Mich.

Pavulon paralyzes the muscles essential for breathing, and causes quick suffocation unless artificial respiration is provided.

Narciso faces one count of murder, one count of conspiracy and four counts of poisoning. Perez is named in one conspiracy count and three poisoning counts.

Judge Philip Pratt, presiding over the complex case, told the jurors to disregard any notion they might have of public opion and to decide the case "regardless of the consequences."

The women face possible life prison sentences. They have said they are innocent of all charges against them.

The jurors must attempt to untangle the confusing and often conflicting testimony of 100 witnesses who appeared during the three-month trial.

Much of the testimony involved obscure points of medicine and science that were extremely difficult to convey to the jurors, none of whom has any medical training.

Since testimony ended last week, the jurors had heard lengthy summations by the prosecution and defense teams. The two sides, of course, molded the mass of scientific circumstantial evidence into two mutually exclusive theories.

Prosecutor Yanko, in his initial summation, asserted that the nurses never intended to kill anyone."On each occasion, there was a safety valve, a precaution, a plan - a means to prevent death," Yanko told the jury.

The precautions failed twice, Yanko said. A 159year-old retired landscaper suffered permanent brain damage from lack of oxygen before he was discovered and revived by doctors. A 73-year-old man died, and Narciso is charged with murdering him.

Federal law permits the charge of premeditated murder, even without specific intent to kill, if a violent act resulting in death is committed with "wanton disregard" for human life.

Yanko offered no theory to explain the purpose of the bizarre behavior he described. He told the jurors they should not even look for a motive.

The prosecution hinged its case on circumstantial evidence that attempted to palce on of the nurses near the alleged victims at that crucial moment. No witness claimed to have seen either woman poison any patient.

The defense, in its summations, argued that the same kind of circumstantial evidence used against the accused nurses could have been used to implicate at least three other hospital staff members, including a nursing assistant who received immunity from prosecution.

The defense attacked the prosecution's failure to propose a motive theory and charged that prosecutors attempted to hide important evidence from the jury.

Edward Stein, a defense lawyer, that suggested that the only conspiracy in the case was carried out by the federal government: "The Veterans' Administration and the FBI and the U.S. attorneys office are trying to solve this problem . . . they're trying to package it nice, neat and tidy - two people, low-level, not citizens."