A federal judge, citing "unfair" conduct by prosecutors, overturned on Friday the conviction of a defendant accused of conspiracy in the 1985 kidnapping, torture and murder of U.S. drug agent Enrique Camarena.

Ruben Zuno Arce, the brother-in-law of former Mexican President Luis Echeverria Alvarez, said he felt "better" on hearing U.S. District Court Judge Edward Rafeedie void his conviction and set a new trial date of July 23.In his decision regarding Zuno's fate, Rafeedie said the government "exploited" the testimony of its key witness in the case and "misled" him into disallowing defense evidence that would have discredited the witness.

"I think it's unfair for the government to have conducted its argument as it did," Rafeedie said. "The amount of evidence in this case against the defendants was minimal. . . . There was not a lot of evidence, and the evidence there was inferential. I am persuaded the trial was unfair as to him (Zuno)."

Camarena was kidnapped off a Guadalajara street Feb. 7, 1985, by members of a drug ring seeking retaliation for U.S. drug raids in Mexico. He was interrogated and tortured over two days and his mutilated body was found in a shallow grave a month later at a ranch about 60 miles outside Guadalajara.

Zuno, 60, was convicted of committing a violent act in aid of a racketeering enterprise, conspiring to kidnap a federal agent and aiding and abetting the kidnapping of a federal agent while he was performing his duties.

Prosecutors accused Zuno of acting as a link between the drug cartel and the highest levels of the Mexican government.

The key witness in the case whose testimony played a role in overturning Zuno's conviction is Hector Cervantes Santos, a former Guadalajara riot police officer.

Cervantes testified that another defendant told him the bodies of Camarena and his pilot were buried on land owned by Zuno.