BOSTON -- In Arizona, Army Pfc Adrian Morris Jr. is going on trial this month for the crime of committing sex. His was not your ordinary fornication and this is not your ordinary court-martial.

Morris is carrying the AIDS virus. More to the point, he knows it. Nevertheless, Pfc Morris had sex with three other soldiers -- one man and two women -- without using a condom and without telling them.

This landmark in the AIDS epidemic is worth noting for many reasons. The Army is trying Morris, it says, because he had sex without protection. Would it have prosecuted him if he had used a condom? Would the crime be more serious if the partners had become infected?

The case is intriguing because Morris was part of something we've heard an awful lot about: a mandatory AIDS testing program.

In the past months, AIDS testing has become anxiety testing or attitude testing. The free-floating concern about the spread of this lethal disease has collected around questions of whether and how and who we are going to test for the virus.

Last week, the president called for testing prisoners and immigrants, people in drug-treatment programs and couples applying for marriage licenses. Two days later the Senate voted to require it for immigrants. The same day the mayor of New York called for tests of all foreigners, even tourists who set foot in his city.

This rush-to-test atmosphere comes with understandable passion. We want to know the unknown. We want a quick way to halt the spread. We want safety. Indeed, those in favor of testing are often seen as protecting the public while those against are seen as protecting the carriers.

It's easy to talk about ''tests'' as if all are equally valuable, and about ''carriers'' as if they all react the same. But it doesn't work that way.

I have no special objection to testing immigrants, although they are not a major source of the disease. Mayor Koch should know the balance of trade in this disease: his city is a greater exporter than importer of AIDS. Nor do I have a deep problem with premarital testing, although again the value seems small.

The most important group, the so-called ''bridge'' into the heterosexual community, the parents of most infected infants, are intravenous drug abusers. Of these abusers, 200,000 may already be infected. Would I routinely offer those who come off the streets to drug-abuse programs an AIDS tests? Absolutely. Would I encourage it? Of course.

But it is not at all clear that the president's way is the best approach to IV drug users -- people who are already involved in irresponsible, illegal activity. There is evidence that drug abusers who test positive for AIDS may behave in ways that are even more irresponsible. It may be foolish to frighten away those who come in off the streets for help.

Something in all this strikes me as particularly odd. While we're focused on mandatory testing, on seeking out carriers as criminals, we are making it difficult for the people most likely to change their behavior, the people who want tests. At testing sites that promise anonymity, the waiting lists are often weeks long. In states and hospitals and college clinics where results end up on permanent medical records -- which in turn affect employment, insurance, even housing -- many shun tests.

Those who favor mass testing and those who harbor reservations do share the same objective: to stop the spread. They are both in favor of identifying carriers and of protecting the public. They differ in beliefs about what works.

Consider the tale of Pfc. Morris again. His case shows the strengths and weaknesses of massive, mandatory testing. The Army's program did not, the prosecutors contend, change his behavior. Nor did it protect at least three Americans from a dangerous carrier. But the testing program did eventually lead to his arrest.

Mandatory testing, with its lists and laws and enforcement, can track down a single offender, or two, or two thousand. But is that an effective health policy in a country where there are now some 1.5 million carriers? It's like stopping a stampede with a pistol.

The questions are less about civil liberties than about efficacy, about the best way to spend our energy and money. It may be comforting to believe that we can get ''them,'' stop ''them.'' But it is confidential and voluntary testing, combined with relentless education and widespread self-protection that can help all of us.