In the videotape, shown in court on Wednesday, Oyler says he was gambling at a casino the day of the fire and was surprised when he saw the blaze on his way home.
"I thought, `Man, that's a hell of a fire,"' Oyler said in the interview with a Riverside County sheriff's detective.
Oyler has pleaded not guilty to five counts of murder, along with multiple allegations of arson and being in possession of destructive devices. He faces the death penalty if convicted.
His attorney says there's no physical evidence linking Oyler to the blaze, and that prosecutors' main witness is more interested in a $500,000 reward than in telling the truth.
Authorities believe Oyler is responsible for an "arson series," that began May 16, 2006, and culminated in the Esperanza fire, which scorched more than 41,000 acres, destroyed 34 homes and 20 outbuildings, killed livestock and damaged a highway.
Oyler has been held without bail in Riverside County jail since his arrest.
The trial is expected to go into the first part of April.
The Associated Press contributed to this story.
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