A jury deliberated for less than a day before finding Scott Weinberg, 52, guilty in connection with an arson spree in September 2009 that damaged several businesses in downtown Walnut Creek.

The Walnut Creek man was convicted of four counts of arson.  He has pleaded not guilty by reason of insanity. During the next phase of the trial, which begin Wednesday, his defense attorney must show that Weinberg was legally insane at the time he started the fires.Weinberg has a well-documented history of bipolar disorder. 

Weinberg  started a fire at the Arroyo Way Comcast offices—causing hundreds of thousands of dollars in damage to computer equipment and temporarily knocking out power to nearly 40,000 cable subscribers. He also was captured on a surveillance video starting a fire at the Wendy's restaurant on North Main Street and was charged in connection with setting a  blaze in a trash bin outside the West America Bank on North California Boulevard.

The Contra Costa Times reported that the defense attorney for Weinberg chose Tuesday not to make an opening statement, which "would have revealed Weinberg's defense."

The Times said that civil court records show that Weinberg has a long history of bipolar disorder, marked by episodes of "unpredictable" behavior.

News reports in September 2009 said that Weinberg had been hospitalized twice because of his illness. He also was the subject of a restraining order to stay away from his second wife and her family because of numerous reports of threats, including to burn down her house, and stalking.

Weinberg had worked at at For Your Eyes Only, a practice in the Ygnacio Valley Shopping Center, from August 2006 until last summer, "when he abruptly quit."

Weinberg remains at County Jail in Martinez in lieu of $1.4 million bail. If jurors find him guilty of the charges, there will be a second trial to determine whether he was legally insane at the time of the fires. 

Determining legal insanity is separate from the question of whether a defendant is mentally ill.

The issue is controversial, although the insanity defense is rarely used.  The theory behind the insanity defense, which goes back centuries, is that someone who is insane doesn't have the intent to commit a crime and therefore cannot be held responsible. But defining insanity, particularly in a legal context,  can be difficult and varies according to state and county. Its definition has evolved over time.

California operates under a definition that goes back to 1840s Britain. The M'Naghten rule says that to establish a defendant is legally insane, it must be proved that the accused was suffering from "such a defect of mind" that, at the time of the crime, he either didn't know the nature and quality of the act or that he did not know what he was doing was wrong.

Deputy District Attorney Simon O'Connell said in his opening statement that there is "no doubt" of Weinberg's guilt, the Times reported. On Sept. 22, 2009, Weinberg started the fire in the trash bin next to the bank after employees said they didn't want him as a customer anymore based on his withdrawal history.  Weinberg targeted Comcast, O'Connell suggested Tuesday, because the cable company recently  had canceled his service.