Lawyers for the Public Defender Service asked the U.S. Supreme Court yesterday to overturn a D.C. law that allows persons found not guilty by reason of insanity to be held in St. Elizabeths for terms longer than the maximum sentences for their alleged crimes.

Their argument came in a case involving Michael A. Jones, who was committed to St. Elizabeths in March 1976 after being found not guilty by reason of insanity on a charge of attempting to steal a coat from a department store. Although the crime itself, a misdemeanor, carries a maximum one-year jail sentence, Jones has been held in the hospital for seven years.

He is allowed every six months to request release, but under the law it is up to him to prove that he is no longer insane or dangerous, and so far he has not succeeded in winning freedom.

PDS lawyers argued that persons found not guilty by reason of insanity may not be confined longer than the maximum sentence they could have received if convicted on the criminal charge, because such confinement violates constitutional rights to due process.

Attorney Silas J. Wasserstrom said that once Jones had spent a year in St. Elizabeths, the government, if it wanted to keep him there, should have had to ask for a civil commitment and bear the burden of proving that he is dangerous to himself and others.

The public defenders' argument is aimed only at those persons confined after pleading insanity in regard to crimes with limited sentences. It would not apply to persons such as John W. Hinckley Jr., who could have faced a sentence of life in prison if convicted, according to PDS lawyer Harry Fulton, who has represented Jones.

PDS lawyers estimate that there are now about 60 persons who have spent more than a year in St. Elizabeths after being found not guilty of misdemeanors by reason of insanity.

Assistant Solicitor General Joshua I. Schwartz argued yesterday that the D.C. law does not violate constitutional rights to due process. The length of a possible sentence, he argued, has no bearing in cases where a defendant decides to plead not guilty by reason of insanity. Schwartz said the government, at a hearing five years ago, met its burden of proving that Jones should be confined.