PHOENIX (Reuters) - Lawyers for Tucson shooting rampage suspect Jared Loughner filed an emergency petition on Friday with a federal judge who already has twice refused similar requests, asking him again to halt the forcible medication of their client with anti-psychotic drugs.

In a 28-page filing, Loughner's defense team urged U.S. District Judge Larry Burns to order that the four-drug regimen administered involuntarily to Loughner be stopped immediately because it violates his constitutional due-process rights.

"There is presently no legal basis -- under any rationale -- to forcibly medicate Mr. Loughner," defense attorneys said in the court documents.

Citing what they said were signs of his improved behavior, his attorneys said Loughner is no longer a danger to himself or others, and therefore the justification for continuing the drugs did not exist.

Loughner, accused of opening fire on January 8 in a shooting spree that killed six people and wounded 13 others, including Arizona Congresswoman Gabrielle Giffords, has received the drugs while being treated at a U.S. Bureau of Prisons psychiatric hospital in Missouri.

The 23-year-old college dropout has been housed at the facility since May, when Burns declared him mentally incompetent to stand trial.

Defense attorneys and federal prosecutors have battled over whether Loughner should be forced to take the drugs for several months, with Burns refusing in June and again in August to halt the treatments.

The 9th U.S. Circuit Court of Appeals heard arguments last month about whether Loughner can be medicated against his will and on the procedures that must be used by prison officials to do so. The three-member panel has yet to render a decision.

Loughner is scheduled to appear on Wednesday in federal court in Tucson for a hearing to determine whether prison doctors should be given more time to restore his mental competency.

Prosecutors claim another eight months is needed to make him mentally fit to stand trial, while defense attorneys object to any time extensions.

Loughner has pleaded not guilty to 49 criminal charges, including multiple counts of first-degree murder.

(Editing by Steve Gorman and Peter Bohan)

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