A U.S. appeals court refused today to overturn the conviction of Charles Edward Neiswender, the New Jersey man found guilty of obstructing justice during the first political corruption trial of suspended Maryland Gov. Marvin Mandel.

The 54-year-old Neiswender had been charged with soliciting a $20,000 bribe from Mandel defense attorney Arnold Weiner, saying that he could influence a juror to hold out for acquittal in the case.

Neiswender's attorneys appealed the conviction, contending that their client's constitutional rights had been violated when he was arrested Nov. 5 outside his New Jersey home, brought directly to Baltimore and taken before Judge John Pratt in a secret hearing. His bail was set at $1 million and he was detained 10 days.

They also had contended that the facts presented in the indictment failed to justify charging Neiswender with obstruction of justice, since Neiswender could simply have been trying to bilk defense attorney Weiner.

In its ruling today, the Fourth U.S. Circuit Court of Appeals said that, even if federal inspectors had violated Neiswender's rights at the time of his arrest, "such violations were essentially technical and nonprejudicial to his defense."

On the question of the indictment, the three-judge panel's oiinion said, "although some ambigulty inheres in the indictment, we find it unobjectionable."

Neiswender, who was sentenced to 2 1/2 years in federal prison, had been free on bail pending the outcome of his appeal, but two weeks ago decided to turn himself in at the Allenwood federal penitentiary, according to his attorney, J. Frederick Motz.

Walter Weikers, a Baltimore man convicted of a separate attempt to obstruct the Mandel case, has finished serving his prison term.

News reports about Neiswender's arrest, coupled with reports of Weikers' attempt to bribe a juror, were overheard by other jurors in the first Mandel trial. This led Judge Pratt to declare a mistrial in the case in December 1977.

Mandel and five codefendants were convicted of mail fraud and racketeering in August 1977 after a second trail. An appeal of this conviction also is pending before the Fourth Circuit Court.