 -- Closing arguments are expected today in the case of a California man on trial for allegedly killing his neighbor, an argument that appears to have started over shrubbery.

Michael Vilkin is accused of fatally shooting John Upton.

Upton, 56, was credited during the 1990s with rescuing hundreds of deformed Romanian orphans, and he was profiled on ABC’s “20/20” for his efforts. He was widely hailed as a hero, but Vilkin called him a bully.

WATCH: Michael Vilkin on Trial in 2013 Shooting

The neighbors had been squabbling for years about Vilkin’s landscaping efforts on a 2.6-acre plot in the affluent San Diego neighborhood of Encinitas. The two were at odds over a narrow strip of land in front of Upton’s front door on Vilkin’s property.

Vilkin, 62, says he bought the gun – a .44 Magnum – after months of arguments and threats, telling jurors Upton, who towered over the diminutive Vilkin, physically and verbally threatened him. He was carrying the handgun immortalized by Clint Eastwood's fictional character "Dirty Harry" with him that day, March 28, 2013.

Vilkin believed his neighbor was armed, but police found no evidence of a second gun at the scene.

"I saw a pistol in his right hand,” Vilkin testified in court. So he said he pulled out the handgun and fired twice, mortally wounding Upton.

While Vilkin claims he was defending himself, Upton’s girlfriend, Evelyn Zeller, disagrees. Zeller told ABC News that her boyfriend was interested in a truce that day, that the couple was planning to move.

"We had found our dream home," Zeller said after the shooting. "'We're out of here,' that's what he went out to say."

ABC News Chief Legal Affairs Anchor Dan Abrams said California’s self-defense law is crucial to the case.

“This is not a particularly strong self-defense case,” Abrams said. “The victim did not have a gun and a prosecution witness says he did not hear any argument or the victim being threatening. And the defendant had a motive; he had a history of antagonism toward the victim.

“So it boils down to whether there’s a juror or jurors who feel that they can’t convict on this evidence.”

Vilkin could face 35 years to life in prison if convicted.