SANFORD, Fla. -

Sanford police officer Chris F. Serino -- the lead homicide detective in the case of the death of Trayvon Martin —testified Monday and Tuesday in the George Zimmerman trial.

In a Seminole County courtroom, he told attorneys that during the investigation he found some of Zimmerman’s behaviors “odd.” He was concerned with him not remembering the names of the streets in the Retreat at Twin Lakes neighborhood, and his concern with going to class the next day.

Special section: George Zimmerman trial

"It just appeared odd that he had that on his mind," Serino said.

During cross examination, defense attorney Mark O’Mara pointed out that Zimmerman seemed relieved at the thought that someone could have recorded the struggle.

 While O’Mara implied that his response was proof of his truthfulness, Serino wasn’t so sure.

It could mean that "either he was telling the truth or he was a complete pathological liar," Serino said. On Tuesday, Judge Debra Nelson asked the jury to ignore Serino's comment regarding Zimmerman's credibility, after De la Rionda pointed out one witness isn't allowed to evaluate another's credibility.

Serino said that at one point during the investigation he learned that the only person who could say with certainty how the confrontation began was going to be Zimmerman.

Zimmerman wasn't always clear during interviews, Serino said. De la Rionda played the recording of an interview that showed an inconsistency.

"I wasn't following. I was just going in the same direction," Zimmerman said in the interview.

"That's following," Zerino said.

Serino said Zimmerman's statement on "these ass#%es, they always get away" could be considered evidence of ill will.

"He was trying to do something in the same direction that Trayvon was going," Serino said.

Serino told attorneys that he thought  Zimmerman's description of Trayvon as "f***ing punks" showed "ill will and spite" and "frustration."

According to ABC News, Serino was the investigator who was unconvinced about Zimmerman's account and initially recommended a manslaughter charge, but the state attorney's office determined there was not enough evidence in the case.