Alleged Killer Acted 'Totally Out of Character' The defense team in the murder trial of a Georgia man accused of killing his alleged lover's husband opened its case today with an emotional testimony from the defendant's sister describing their troubled childhood and her brother's "totally out of character" behavior in recent years. Hemy Neuman, 49, is charged with shooting and killing Andrea Sneiderman's husband, Rusty Sneiderman, 36, in the parking lot of the Sneidermans' son's preschool in November 2010. Neuman, Andrea Sneiderman's former boss at GE Energy, has pleaded not guilty by reason of insanity. His younger sister, Monique Metsch, was the defense's first witness today. Much of her testimony centered around the violent childhood she said they shared because of an abusive father. "He was a very angry man, so there was always fights or screaming," Metsch said. You never knew how he was going to react. He was very erratic in his outbursts. We never knew how the evening was going to go. Neuman's defense attorneys said in their opening statements that Neuman's rough childhood was the start of his mental illness. I would blame everything on Hemy, so the hand would go â¦slaps that were continuous. He would hit with an open hand," Metsch said. I've been kicked. I've been slapped. I've been whipped. The attorney asked whether all those things also happened to Neuman, and Metsch said yes, "if not a lot more." Metsch described an incident when she was about 7 and said a bad word while riding in a car with her father and brother. Her father asked who taught her the word, and she said that Neuman had. "It didn't take one second for him to pull over, literally drag [Neuman] out of the car, pull him out of the car, lean him against the car and start beating him over and over and over again," Metsch said. Neuman put his head down in the courtroom at this point of the testimony. Metsch also described the struggle of growing up with a gorgeous but absent mother and how her brother was a bright student, while she flunked several grades. The judge stopped the testimony to ask why it was relevant to the case, and the defense changed the subject. Metsch later recalled visiting her brother and his family in 2008. She had heard from Neuman's estranged wife, Ariella "Reilly" Neuman, that the couple were having financial problems, and Metsch said her brother was acting "totally out of character" during the visit. Despite the money troubles, he was having a waterfall built in the yard, throwing an extravagant party for his children, offered to pay for Metsch's airfare and his wife had a new diamond ring, she said. At one point during the visit, she said, Neuman "exploded" at his mother. "If he could've made her feel smaller than a granule of sand, then that would be how he made her feel," Metsch said, tearing up as she recalled the outburst. Everybody felt very uncomfortable. Ariella Neuman does not believe that the erratic behavior suggests her husband was mentally ill, according to her attorney Esther Panitch. The estranged couple have been married for 23 years and have three children together. "My client did not see any signs of a mental illness, just the many signs of a man caught cheating," Panitch told ABC News. On another visit in December 2010, Metsch remembers her brother talking about a colleague in Atlanta, presumably Andrea Sneiderman, with whom attorneys allege he was having an affair. Sneiderman denies the affair. "He told me that he had befriended a colleague of his and that he had become close with her in the sense that, for the first time, he was able to really open up to someone about our childhood and talk," Metsch said. He realized for the very first time that he didn't have that kind of communication with Reilly, but that this relationship was special because of that. Neuman told his sister in late December 2010 that he was considering suicide. "He told me he was very depressed, going through very difficult times," she said. He had been thinking about suicide. A forensic psychiatrist, Dr. Julie Rand Dorney, who spent three hours meeting with Neuman in jail to assess his mental state, also testified today, telling the court that she chose not to accept any money for her consultations for this case. Dorney acknowledged on the stand that "when there's a murder charge, there's an incentive to exaggerate symptoms," so she wanted to meet with Neuman to see whether he was faking his alleged mental illness. When asked about her findings, Dorney said Neuman was "severely depressed," was experiencing "severe marital discord" and was stressed about finances and a bad review at work. He also said that Neuman had considered suicide. Neuman told Dorney his outlook changed when he met Andrea Sneiderman in April 2010. "He felt moments of joy, connected, like he had feelings again," Dorney said. [He] then became very obsessive and would ruminate about that relationship â¦ hard to tease apart how much fantasy or reality. Dorney said that what Neuman told him about his relationship with Sneiderman was "confusing." He talked to Dorney about his obsession with her, but his testing showed "some possible psychosis," so Dorney did not know whether the affair was real or not. "[Neuman] would at one point say he had sex with this woman and at later points when I asked him if he was having an affair with her, he would say, 'I don't know, I guess if she says it didn't happen, I guess it didn't happen,'" Dorney testified. Christina Ng contributed from New York.