Arguments continued Thursday in the trial of Jeremy Martin, 37, who is accused of killing his father with a shotgun at their Huntington Beach home two years ago.

Martin is charged with one count of murder and, if convicted, faces 50 years to life in prison, according to a news release from the Orange County district attorney.

Martin allegedly shot Frederick Martin, 62, after Huntington Beach police visited them on the morning of May 20, 2011.

Martin's mother, Gerry Martin, took the stand Thursday to answer questions about her son's past behavior.

After sitting basically motionless during earlier testimony, Martin began to shake his leg and brought his hands to his eyes as his mother was sworn in.

In a shaky voice she told the court of a time when Martin was in his early 20s and she found him in an agitated and paranoid state. She said she knew he had been smoking meth since he was about 18, and on this day she heard noises coming from his room. She entered and found him with his head in his hands and he said, "They're trying to get me. A helicopter landed on the roof and aliens are trying to kill me. Mom, please, help me, help me."

"I can remember it like it happened yesterday," she said.

Later on cross examination, Senior Deputy District Attorney Sonia Balleste asked Gerry Martin if she had a preferred outcome of the trial. The witness fell silent and sat motionless for a full 60 seconds. With the courtroom waiting in silence Gerry Martin answered, "I think he probably needs to serve time for drug charges."

Testimony early in the day and late Wednesday by forensic psychologist Michelle L. Vorwerk surrounded the idea of amphetamine-induced psychotic disorder. Defense attorney Stephen Daniels and Balleste asked the expert witness about how she determined Jeremy Martin's behavior on May 20 was amphetamine-induced psychotic disorder.

Vorwerk said she based her diagnosis on records of police interviews, the fact that meth was found in the suspect's room and what she read from interviews of the family, as well as what Martin told her.

She said police reports indicated Martin was talking to himself and was acting paranoid.

Daniels asked if testimony by one neighbor that they heard "You son of a bitch, you tried to have me murdered last night" and another that said she heard a voice yell, "You tried to have me killed," helped lead her to her conclusion of a drug-induced psychosis.

Vorwerk also said when Jeremy Martin was off drugs for a period of years, he did not display erratic behavior that she would expect from someone with a mental disorder.

Jeremy Martin and his father allegedly got into an argument May 20 because the son was keeping a firearm inside their home.

Frederick Martin called police to have them evaluate the mental state of his son, according to the release, but he didn't mention to police that they were in an argument about the firearm.

Police came to the house, but Jeremy Martin reportedly refused to talk with them.

After police left, Jeremy Martin allegedly shot his father once, and Frederick Martin died at the scene, according to the district attorney's office.

According to the release, Jeremy Martin called 911 and reported that he shot his father.

The trial is expected to continue with closing arguments Monday at the Central Justice Center in Santa Ana.

alicia.lopez@latimes.com

Twitter: @alicialopezHB