UNITED STATES (REUTERS) - The trial began on Monday (Oct 23) for Jose Ines Garcia Zarate who is charged with second-degree murder for fatally shooting Kate Steinle.

Steinle was shot on a San Francisco pier in 2015 with what officials said was a stolen gun.

Her death has put immigration laws into the national debate long before Monday's opening arguments.

"This very well could be an accidental shooting," said Defence Attorney Matt Gonzalez.

Defence Attorney Matt Gonzalez says his client found the gun wrapped in a t-shirt and it then went off, denying allegations by prosecutors that Garcia Zarate was recklessly pointing the gun at people on the pier.

"If he didn't know that the object he touched had a gun in it, then he does not bear criminal responsibility," added Gonzalez.

Garcia Zarate reportedly had been deported to Mexico five times since first entering the US as a juvenile.

Steinle's shooting prompted the US House of Representatives to pass Kate's Law to increase penalties for illegal immigrants who return to the US.

President Trump has repeatedly cited the case as an example of the dangers posed by lax border security and cities that refuse to comply with certain federal immigration laws.

Garcia Zarate has pleaded not guilty. He faces 15 years to life in prison if convicted.