Lawyers for Jose Ines Garcia Zarate filed court papers arguing that the judge failed to properly instruct jurors before they found him not guilty last month of killing Kate Steinle on a popular pier in 2015.
Jurors did convict him of being felon in possession of a firearm. Garcia Zarate has previously been convicted of illegal re-entry into the United States and had been deported five times before Steinle was fatally shot.
The San Francisco sheriff's department released him from jail several weeks before the shooting, ignoring a request from federal immigration officials to detain him for a sixth deportation.
San Francisco's sanctuary city policy bars local officials from helping federal immigration authorities in deportation matters unless they have a warrant. Donald Trump pointed to the shooting during his presidential campaign as another reason to build a wall along the Mexican border and tighten immigration policies.
Defense lawyers argued in court papers that the judge improperly barred the jury from considering Garcia Zarate's claim that he didn't know he was holding a gun when it fired. They also argue that Garcia Zarate didn't hold the gun long enough to warrant a firearm possession conviction.
Jurors had asked for clarification during deliberations on what "intent" they had to determine from Garcia Zarate to convict him of illegal possession.
Garcia Zarate said he was sitting on a city pier when he found and picked up a gun wrapped in rags. His lawyer said Garcia Zarate didn't know it was a weapon until it accidentally fired, the bullet ricocheting of the pier's concrete walkway and striking Steinle in the back.
The motion for a new trial will be considered Jan. 5. If it's denied, Garcia Zarate is scheduled to be sentenced that day. The San Francisco district attorney's office declined to comment Thursday.
Garcia Zarate faces a maximum sentence of three years in jail. He has been in the San Francisco jail since his July 1, 2015, arrest.
A federal grand jury recently indicted Garcia Zarate on two felony charges of illegal gun possession. The San Francisco sheriff's department said it will turn him over to federal authorities after he has finished his state sentence.
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