A federal appeals court upheld yesterday the 1983 conviction of Mary Treadwell, former head of the D.C. Youth Pride job training program, for conspiring to defraud the federal government in connection with the management of the Clifton Terrace Apartments.

A three-judge panel of the U.S. Court of Appeals rejected arguments by Treadwell's attorneys that prosecutors had failed to present sufficient evidence to prove their case during the month-long trial.

The 29-page opinion by appeals court Judge Edward A. Tamm also found that U.S. District Court Judge John Garrett Penn had properly instructed the jury and said it was a "harmless error" that a one-page document not offered into evidence was "inadvertently" included in the mass of papers sent to the jury.

The appeals court noted that when the jurors found the document, which summarized the testimony of an FBI agent, during the sixth day of their 20 days of deliberations, they notified Judge Penn, who retrieved the paper and instructed the jurors to disregard it.

The opinion found that the document was "merely cumulative" of evidence that was properly admitted and ruled that the jury did not consider it in their deliberations.

Under court rules, attorneys for Treadwell may now ask the appeals court panel to reconsider its decision or may seek a hearing before the full 11-member appeals court. Treadwell can also take the case to the U.S. Supreme Court.

Her lawyers could not be reached for comment last night.

Treadwell, 44, is free without bond, pending the outcome of her appeals.

She was sentenced last year by Penn to three years in jail and fined $40,000.

Treadwell, a former wife of D.C. Mayor Marion Barry, was found guilty of conspiring to defraud the federal government and the tenants of Clifton Terrace, a low-income apartment complex on 13th Street NW, of thousands of dollars to enrich herself.

She also was convicted on seven counts of making false statements about the management of the apartments to federal officials but was acquitted of 13 other charges.

P.I. Properties, a corporation set up to buy Clifton Terrace from the federal government, was headed by Treadwell. The company owned the apartments from 1974 to 1978. Treadwell contended during the trial that she had no knowledge of any wrongdoing.

Misuse of Clifton Terrace funds was first disclosed in a series in The Washington Post in 1979, which lead to a two-year federal investigation and eventually to Treadwell's trial. She was the fourth and last defendant sentenced in the case.

Besides Tamm, the other members of the appeals court panel that ruled yesterday were Judges Robert H. Bork and Carl McGowan.