SAN FRANCISCO (CBS / AP) — A judge says he’s skeptical of a Mexican national’s claim that he’s a target of a vindictive federal prosecution because a San Francisco jury had acquitted him of murder in a case at the center of a heated national debate over immigration.

U.S. District Judge Vince Chhabria said Tuesday that Jose Ines Garcia-Zarate faces an uphill battle proving federal gun charges were brought solely because of politics.

A San Francisco jury acquitted Garcia-Zarate of murder in the July 2015 shooting death of Kate Steinle on a San Francisco pier.

He had been released from jail weeks earlier despite federal immigration request to detain him for deportation. San Francisco’s so-called sanctuary city policy bars local cooperation with federal deportation efforts.

Federal officials charged him with illegal gun possession five days later.

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