The Supreme Court declined yesterday to rule on a controversial right-to-bail case, in an opinion that almost guarantees that the sensitive issue will not be decided by the court for a long time.

The justices said the case, involving a Nebraska constitutional amendment denying bail to defendants charged with forcible rape, was moot.

In an unsigned opinion with one dissent, they said the defendant who brought the case has since been convicted of rape, sentenced to prison and couldn't get out of jail no matter how the justices ruled on his pretrial detention.

The court's action yesterday is part of a pattern of controversy-dodging by the court in recent months.

Last week, the justices sidestepped a ruling involving the right of municipalities to close video arcades to those under the age of 17. Last month, the court avoided deciding an important case concerning free speech rights at private colleges. Last year, more than a dozen major cases, including an affirmative action issue, went undecided on relatively technical grounds.

These actions are not considered technical by some of the justices, who regard mootness and other similar matters as important controls on the caseload of the federal judiciary.

But as applied to the Nebraska bail case, the mootness reasoning makes it much more difficult for anyone to challenge preventive-detention laws. Because of the time consumed by the process of appealing to the Supreme Court, which can involve several years, it is likely that a defendant denied bail under a preventive detention law will have been convicted or acquitted by the time the court gets his case. It is likely, therefore, that the bail issue will always be moot.

The court tacitly acknowledged as much in its six-page ruling yesterday. The justices suggested that a class action, a challenge on behalf of future defendants held without bail or a damages suit against denial of bail might be the only way an appeal could reach the court without being moot.

The court wiped out, on grounds of mootness, a ruling of the Eighth U.S. Circuit Court of Appeals holding the Nebraska provision unconstitutional. That means the Nebraska amendment is reinstated.

Yesterday's action appeared to doom chances that the court will rule soon on the District of Columbia's preventive detention law. A ruling upholding the constitutionality of that statute was awaiting Supreme Court action in the Nebraska case.

The court knew the status of the Nebraska defendant, Eugene L. Hunt, when it accepted the case this fall. The decision to avoid a ruling on this controversial subject was an option the justices could have exercised at that time.

Only Justice Byron R. White dissented yesterday. He said the justices should allow the Eighth Circuit appellate court to sort out the question of mootness.

It was significant that the court's staunchest liberals--Justices William J. Brennan and Thurgood Marshall--did not dissent from the unsigned opinion. Civil liberties lawyers speculated that Brennan and Marshall, along with liberals generally, would prefer that the increasingly conservative Burger-Rehnquist court avoid issuing sensitive opinions that could influence the law for the next generation.

The court did rule yesterday on a case involving attorneys' fees in civil rights cases. The court unanimously held that requests for fees, which may be awarded by a judge to a successful plaintiff, do not have to be submitted within a certain time limit.

In White Vs. New Hampshire Department of Employment Security, the court reversed a lower court ruling that deadlines for filing certain motions in a case also served as deadlines for legal fee submissions.