Federal prosecutors, armed with technical laboratory evidence and complex medical testimony, are attempting to prove that two nurses used a new paralyzing drug to murder and poison critically ill patients at the Veteran Administration Hospital in Ann Arbor, Mich.

The case in U.S. District Court here was recessed two weeks ago after six weeks of testimony from 67 witnesses - doctors, nurses, laboratory scientists and relatives of the stricken patients. The trial of the nurses, who have pleaded innocent, resumes today.

Roger W. Aaron, an FBI analytical chemist from Washington, D.C., has testified that he had developed a series of tests to isolate and identify the relatively new and unknown drug Pavulon in embalmed human tissue.

Pavulon paralyzes the diaphragm and other muscles involved in breathing. A small dose can cause almost instant suffocation if artificial respiration is not immediately provided.

Aaron's testimony, illustrated with elaborate charts and graphs, took two days. It clearly strained the fury's ability to concentrate. But its complexity was indicative of the kind of evidence the prosecutors must use if they are to prove that a 1975 epidemic of sudden breathing failures among hospitalized veterans, most of them in the VA hospital's intensive care ward, was not the result of natural cases.

Today the prosecution will begin to examine in detail the chaotic events of Aug. 15, 1975, when five patients suddenly stopped breathing within a single hour.

The accused nurses - Filipina Narcisco, 30, and Leonora Perez, 32, who emigrated from their native Philippines six years ago with plans of becoming U.S. citizens - face possible life prison terms.

But the verdict is unlikely to settle the political, social and medical controversies that have surrounded this highly publicized case for the last two years.

The prosecution charges that Narcisco and Perez murdered two patients and poisoned seven others at the VA hospital during that summer by injecting Pavulon or a similar drug into the intravenous tubes that fed nutrients and medication directly to the men's veins. The women also are accused of conspiracy to poison the hospitalized veterans.

The prosecution's review of the crucial period between 4:40 and 5:50 p.m. on that hot summer evening is expected to take two to four weeks. More than 40 witnesses will be called.

Then the defense team will begin a presentation that is expected to last as long as a month.

It will probably be July before Judge Philip Pratt delivers the final instructions to the jury.

The charges stem from an outbreak of more than 50 sudden breathing failures that struck 35 patients during July and August, 1975. Most of the victims were quickly resuscitated, but there were 11 deaths associated with the breathing failures and investigators came to believe that at least six of the dead were murder victims.

The FBI has contended that many of these breathing failures were caused by synthetic version of curare, the potent vegetable-derived nerve poison developed centuries ago by South American Indians for use on hunting arrows.

The nurses have said they are innocent, and a sizeable number of people have organized in the United States, Canada and the Philippines to support them.

These supporters, operating principally in Chicago, Ann Arbor and Manila, have raised and spent a defense fund of more than $100,000. They also have raised strident charges of racism and sexism against the federal prosecutors and the FBI, which have jurisdiction over the case because the alleged crimes were committed on federal property.

Federal authorities have denied the charges of bias and misconduct.

Assistant U.S. Attorney Richard Yanks has accused the nurses of committing "sordid" and "evil" acts.

But Yanko also acknowledged that he has no eye-witnesses, but only circumstantial evidence to place the accused nurses near patients around the time of alleged drug attacks. He also proposed no motive to explain the strange conspiracy he described.

Defense attorney Thomas O'Brien suggested that three other persons should be suspectes in the crime.He said the defense would come closer than the FBI in solving the hospital mystery.