With a new season of congressional hearings about to begin on virtually every infirmity, hope and anxiety of people and society, it is desirable to examine that peculiar breed of testifiers known as expert witnesses.

Nuclear, metallurgical, sociological, interplanetary, economic, psychological and on down the line of specialties and sub-specialties that reflect the splintered character of contemporary scholarship, experts by the platoon are ticketed for or on the way to the capital. Their presumed object, of course, is to bring enlightenment to the political process, but, in fact, the ultimate product of most expert testimonies is an additional ration of confusion for issues that were none-too-lucid to begin with.

The reason, first of all, is that uncommitted, disinterested experts -- who are very rare, indeed -- tend to be cautious and tentative when addressing the scientific or technical components of political issues. This puristic quality has its merits, but it doesn't mix well with the political urge to get on with doing something about the problem under discussion. This accounts for Sen. Edmund Muskie (D-Maine) once saying that he craved the appearance of some one-armed scientists so that he could be relieved of "on-the-one-hand, on-the-other-hand" explanations.

Far more prevalent than those who try to stick to the facts are the committed specialists. Identified with issues that range from nuclear power to nutritional labeling, their object is not so much to produce the facts as it is to move the cause. When they give congressional testimony, as they often do, the quasi-judicial setting of the hearing room creates an illusion of carefully accumulated and verified data being presented to a comprehending and authoritative body. The reality, however, is that most hearings are pre-programmed dramatic presentations, rather than free-ranging inquiries. And it's the political or ideological predisposition of the reigning chairman that determines which experts are going to get the spotlight.

This doesn't mean, however, that only one side receives attention. Opposing committed experts try to stay aware of each other's movements, so that even if uninvited to a public performance, they can let loose a countersalvo. Thus, if expert witnesses tell a sympathetic congressional subcommittee tht substance X is a peril to public health, the producer's experts will hurry forth with a contrary pronouncement.

What has happened with scholarly expertise is that it has been subsumed by political operators who recognize the value of professorial endorsements and denouncements. Name the object, and from this courty's many and ideologically diverse scholarly and professional communities, it is not at all difficult to obtain supportive expert testimony.

The conscription of scholarship for political purposes enlivens the question of how to get at the scientific and technical realities inside political issues -- say, for example, nuclear safety or the related issue of how much coal combustion the atmosphere can safely absorb.

The answer is that it's not easy and it's going to become more difficult as the stakes on such issues become bigger. More so than any other institutions, universities were once safe havens for independence that could be called to public service. But, with academe desperately looking to government, industry and wealthy patrons to help it ride out a seemingly interminable recession, our campuses are no longer the bastions of independence that they once were.

Whom should we trust on matters that are beyond lay knowledge? Increasingly, the answer is that, individually and institutionally, we chose our experts on the basis of their politics, rather than on the quality of their expertise.