A San Luis Obispo man was living in a fantasy world, but he wasn’t delusional when he gunned down his mother, a psychiatric witness testified for the prosecution Tuesday.

Based on his review of the evidence and more than three hours he spent with the defendant, forensic psychologist Kris Mohandie told a jury that Christopher Shumey was not legally insane when he murdered Karen Shumey, 65, of Arroyo Grande, on Sept. 17, 2011.

“It was overwhelmingly clear that he knew what he was doing,” Mohandie said.

Shumey has already been convicted of second-degree murder in the death of his mother. The second trial now being conducted is to determine his sanity at the time of the slaying.

Defense witnesses previously noted that Shumey has had a mental illness since 1999, when he was a senior at UC Santa Cruz. But Mohandie said Shumey has exaggerated his symptoms in order to get a verdict of not guilty by reason of insanity.

“I’m not saying he doesn’t have a mental illness,” Mohandie said. “What I’m saying is he’s grossly exaggerating how that impacted him at the time.”

Mohandie recently testified in three other local insanity murder cases. He testified that John Woody, who stabbed a stranger to death at a Paso Robles Laundromat, and Kenneth Cockrell, who killed his wife with a hammer, were both sane at the time of their crimes. In the trial of Andrew Downs, who murdered two women in Santa Margarita, he concluded the defendant was legally insane.

During his interview with Shumey, he said, the defendant acted as if he was hearing voices, but he thinks Shumey was faking.

“To me, it didn’t seem like he was having auditory hallucinations,” he said. “It seemed like it was rather theatrical.”

Shumey’s demeanor changed, he said, whenever he turned a video camera off. And his symptoms seemed to subside once their interview was over.

Defense attorney Pierre Blahnik said that in the 15 years since Shumey has been diagnosed as mentally ill, Mohandie is the only expert to suggest he was malingering, the psychiatric term for exaggerating or faking symptoms. And previous defense witnesses testified that Shumey has experienced hallucinations in the past and kept a composition book in which he wrote to celebrities and people he’d made up.

While Blahnik has said that Shumey suffered from delusions when he shot his mother, Mohandie said Shumey had an active fantasy life, which didn’t meet the standard for delusions.

Furthermore, his actions on the day of the shooting suggest Shumey knew what he was doing.

Telling police he knew he’d killed his mother, Shumey recognized what he did and knew it was wrong, Mohandie said. Later, he expressed shame when he said he didn’t deserve to eat.

While others have diagnosed Shumey with schizoaffective disorder, Mohandie thinks he was bipolar with depression at the time. On the day of the murder, he said, Shumey wanted to kill himself but was interrupted by his mother’s visit.

“The desire to kill himself became a homicidal impulse,” he said. “He was angry at her for interfering with his suicidal plan.”