"THE JUSTICE Department," charges Sen. Howard Metzenbaum, "seems to think that all the poor people ought to go to jail while the rich people go to their country clubs." That off-the-wall statement accompanied last week's announcement that the Senate Judiciary Committee would undertake an investigation of the department's handling of certain white-collar crime cases involving large corporations. The attorney general quickly countered in defense of the department, professing nevertheless that he welcomed the investigation as the "ideal forum" in which to examine the record. We don't take at face value either Mr. Metzenbaum's hyperbole or Mr. Meese's professed enthusiasm for the hearing, but we do think it's a good idea. There are serious matters to be considered.

The common thread that unites the cases at issue -- E. F Hutton, SmithKline, Eli Lilly, General Dynamics and General Electric, to name a few -- is the allegation that corporate officers are not being vigorously prosecuted individually for wrongdoing by their companies. Some of the cases are still in progress, but others have been settled, usually with the corporation's paying a large fine and the officers' being penalized lightly, if at all. The Judiciary committees in both houses -- the House subcommittee on crime began its investigation last spring -- are the right forums for these inquiries, since they have oversight responsibility for the Justice Department.

If political influence has been brought to bear in these criminal cases, that would be a major scandal. It is more likely that investigations will focus on less spectacular but important questions of general policy and on specific decisions. Justice Department officials say, for example, that they could not prosecute individuals in the Hutton case because, in an effort get evidence about participation of the company's top executives, they granted immunity to regional and branch managers who turned out to be the real culprits. The best to be said about that is that it was a mistake. Or was it worse than that? Congress should satisfy itself on the answers.

Prosecutors, it is true, necessarily exercise a great deal of discretion. Every potential case must be evaluated in terms of the importance of the offense, the evidence available and the wisdom of granting immunity in return for testimony. Government attorneys also have to consider the alternative benefits of accepting a plea to avoid a costly, time-consuming and possibly unsuccessful trial. Even if there is no conspiracy in the Justice Department to leave wealthy wrongdoers to their country clubs -- this department, after all, prosecuted Paul Thayer, a corporate mogul and administration big shot, and sent him to prison on securities charges -- what remains is the essential question of how that discretion was exercised. For everyone's peace of mind, the Judiciary committees should find out.