Reporter: One year after blowing away his neighbor with a cannon of a handgun, Michael vilkin is on trial. The stakes are high. A total of 50 years to life if convicted of first degree murder. But... See More
Reporter: One year after blowing away his neighbor with a cannon of a handgun, Michael vilkin is on trial. The stakes are high. A total of 50 years to life if convicted of first degree murder. But vilkin is unfazed. He's confident that this was no murder, but an act of self-defense. This case was justified. Self-defense. Mr. Vilkin protected himself. You have to wonder whether vilkin saw himself as sort of a modern-day dirty harry, out there to protect himself against the D guy in defense of a principle. Go ahead, make my day. He told me, "You are a fanatic." The way he looked at me would fry a hamburger. He loved owning that land. Reporter: The defense strategy was to put the victim on trial. According to vilkin, his neighbor John Upton, seen as a saint for his selfless work rescuing abused orphans in Romania, had a volcanic temper which had been erupting on vilkin with increasing ferocity as vilkin pursued his assault on those trees. The heart of the defense here was that Upton was a threat to vilkin, that he wasn't just this lovable, friendly guy, but he was an angry, aggressive guy who came after vilkin. My body language was -- don't cut the trees here! When he was talking to me angrily it was like, "Uh!" Reporter: But what had transformed Upton from a global do-gooder to the ogre next door? Remember, he didn't even own his home. He was just renting. The trees were on vilkin's property and he had every right to cut them down. This was his land! Reporter: The issue is that, for Upton, those Brazilian pepper trees weren't just pretty, they provided him and his girlfriend Evelyn Zeller precious privacy. He took privacy away. Wow, do you really need to cut these trees down, too? I mean you'll see how it looks. Reporter: Rising in the witness stand, vilkin demonstrates how Upton would get in his face. Stop cutting trees! Reporter: And vilkin had a powerful witness to attest to this ugly aspect to John Upton's character. I would say John Upton was a bully, a dominant, controlling kind of guy, liked to get into people's business. Reporter: Did he get in your business? Yes, he did. Reporter: Duane Byrum is the ex-husband of Upton's girlfriend Evelyn Zeller. When I was dropping off my kids, he'd get in my face. Get the Back to the car, back to the driveway, you have no right to come to my house. Reporter: Byrum says the verbal abuse was withering and unprovoked. You're a . You're a . Get the Out of here. I believe John Upton had a dark side. Reporter: And so when you hear Michael vilkin talking about being physically intimidated frequently by John Upton, you're saying that's within the realm of reason? Yes. Absolutely. Reporter: A sheriff's deputy testified that exactly one week before the homicide, vilkin called for help because Upton's vehicle was parked on vilkin's driveway, where he wanted to work. Got angry, said, don't get closer to me, something like that. Reporter: In fact, vilkin made several calls to the sheriff's department for help dealing with John Upton, but profanity is not against the law. And Upton made no specific threats. There was nothing the authorities could do. He did not threaten to break my neck. He did not threaten to break my legs, but I was afraid of him. Reporter: Afraid, but not deterred. Vilkin stood his ground, continuing to cut away at those trees while also purchasing that fateful .44 magnum and warning the uptons to steer clear. I nailed a sign. The sign said "No parking" on the 30 feet road. Reporter: But, was vilkin secretly plotting something sinister? Two day laborers whose faces we were not permitted to photograph testify that on the morning vilkin went ballistic, they saw him carrying this gun case when he instructed them to remove the Brazilian pepper trees on the driveway where Upton's car was parked. He told you that if someone came out, don't worry about getting involved. He'll take care of it. Correct? Yes. That's right. He was told, basically, "Don't get involved in anything." Mr. Vilkin indicated that if somebody comes out, he had a gun for them. Reporter: Vilkin then retreats some distance up the driveway to a partially obscured vantage point along the fence. Some would say you were lying in wait. If I wanted to wait for him, I would not cut bushes. I would grow the bushes and with a rifle I would wait in the bushes. Reporter: And sure enough, within minutes, Upton emerges from his home. And he told you he was going to move his car? Correct? Yes, that's right. I was afraid of John Upton. I was just very concerned he might do something, something very dangerous. I took the gun out of the gun case and stuck it in the waistband. Why? I was getting ready for eventual confrontation. Reporter: The prosecution had already put on a parade of witnesses to show premeditation -- sheriff's deputies who vilkin contacted five times with questions about his right to carry a gun and stand his ground on his land. He was asking when it was legally justified to carry a firearm on his property and when he was justified in using it. Reporter: Ironically, no witness may have been more damaging to the defense than vilkin himself. Detached, showing zero empathy for his victim. He cooly recounts the morning of March 28th. John Upton came out of his house and bullied him for the last time. When he was about ten feet away I saw a pistol in his right hand. It was like one second. And I pulled out my revolver and shot him. Reporter: But in fact, there was no pistol in Upton's hand. Just a blackberry. As a practical matter, in a case where you're claiming self-defense, with these facts, vilkin almost had to testify. And yet, he was a pretty terrible witness. Vilkin's attorney Richard berkon argues it was self-defense. Remember, vilkin did not run. He stayed and called 911 himself. He could've planned this in such a way that he could've been on a plan to Russia before anybody showed up. But he stood there and he stuck around because he believes and knows he did what he had to do. Reporter: As the trial winds down, tamara vilkin's faith in her husband and god remains unshakable. I think everything is in god's hands. Whatever he decides. Reporter: She waits for justice in the sweltering heat of this lonely parking lot outside the jail. And he stood before the angel. Reporter: As she reads the bible, we visit with the man who thought he could skip that part about "Thou shalt not kill." Mr. Vilkin, hello. Hello. Reporter: Are you hopeful? I'm always hopeful. Reporter: But would the jury see a man just trying to stand his ground, or a stone cold killer?
This transcript has been automatically generated and may not be 100% accurate.