Ingmar Guandique, convicted of killing intern Chandra Levy, returned to Washington on Thursday to ask a D.C. Superior Court judge to order a new trial.

Guandique’s public defenders told Judge Gerald I. Fisher that a new trial is warranted because of new information that prosecutors received about a key witness.

It remains unclear what the new information is or why Guandique’s attorneys think it merits a new trial. Fisher, at the request of the prosecution, ordered all documents sealed and two hearings closed. All the attorneys in the case are under a gag order.

Prosecutors argued Thursday that the new information should be sealed because of safety concerns for the witness. Fisher agreed, and he ruled that future proceedings will remain closed.

Separately Thursday, the D.C. Court of Appeals denied a request to unseal the new information. The panel ruled that keeping the documents sealed is constitutional because it is for a limited time to protect the safety of a witness.

This undated file photo released by the family shows Chandra Levy. (Modesto Bee/AP)

Guandique was flown from a federal prison in Alabama to attend the hearing, his first since being sentenced to 60 years in prison. Looking slightly thinner than he did during the 2010 trial, Guandique, 30, was escorted into the courtroom with ankle and leg shackles, a shaved head, mustache and goatee. Security in the courtroom was heightened, with visitors required to submit to additional security checks and searches.

Guandique nodded when Fisher greeted him. He wore headphones to listen to a Spanish translation of the proceedings for him.

Guandique, a Salvadoran in the United States illegally, was convicted of first-degree murder after a high-profile, eight-week trial. The case drew national attention because Levy, who was killed in 2001, had been having an affair with then-Rep. Gary Condit (D), a married congressman from her home town in California.

A coalition of newspapers and media outlets, including The Washington Post, asked for the documents to be unsealed and the hearings opened.