Judge declares mistrial of U.S. border agent

PHOENIX (Reuters) - A judge declared a mistrial due to a deadlocked jury on Friday in the case of a U.S. Border Patrol agent charged with killing a Mexican man crossing illegally into Arizona.

U.S. District Judge David C. Bury canceled the trial of Border Patrol agent Nicholas Corbett after the jury had failed to reach a verdict since starting deliberations on Tuesday, a court official said.

Corbett, 40, faced charges of second-degree murder, manslaughter and negligent homicide for shooting dead Francisco Dominguez Rivera on January 12 2007, in a case closely watched by watched by pro- and anti-illegal immigrant groups.

The shooting occurred on an isolated stretch of the border between Naco and Douglas, where Dominguez Rivera, 22, had crossed from Mexico with his two brothers and the girlfriend of one of the brothers.

Corbett said he fired after Dominguez Rivera threatened him with a rock, while prosecutors argued the shooting was unprovoked.

The incident drew an immediate rebuke by the Mexican government last year with that country's Foreign Ministry complaining of "disproportionate violence." Diplomats at the Mexican Embassy in Washington called for a thorough investigation.

Two years ago, two Border Patrol agents in Texas were tried for shooting an unarmed Mexican drug smuggler in the buttocks in a case that drew widespread attention. Ignacio Ramos received 11 years and a day in prison and Jose Alonso Compean was sentenced to 12 years.

(Reporting by David Schwartz, writing by Tim Gaynor, editing by Bill Trott)