WASHINGTON — Salvador Martinez, a one-time paralegal and three-time convicted felon, wants to represent himself in appealing his 1998 conviction for stealing $6,000 while working for a Santa Ana law firm. But his court-appointed Washington, D.C., lawyer made little or no headway Tuesday in persuading the U.S. Supreme Court to let him.

Justices across the ideological spectrum showed scant interest in the argument that a convicted defendant has a constitutional right to represent himself on appeal — just as a defendant can do at trial.