"It doesn't become an investigation until we believe a crime has occurred," Demerjian said.
His office opened the case on Oct. 29, three days before the election, after receiving a letter of complaint.
A week earlier, Jane Barnett, the head of the Los Angeles Republican Central Committee, sent a letter to county Dist. Atty. Steve Cooley outlining her concerns.
Barnett said Gatto has listed an address within the district — which includes Silver Lake and other northeast Los Angeles neighborhoods, as well as Glendale and Burbank — on voting records since 2004. But she cited political donations from Gatto to Rep. Brad Sherman (D-Sherman Oaks) in 2008 that list an address on Canyon Drive in Hollywood, which is outside the 43rd Assembly District.
Gatto, an attorney, is also listed at the Canyon Drive address as the legal agent for a mortgage lending company.
"Since Mr. Gatto was apparently registered and voting at one location but living at another, I am concerned that there may be potential voting irregularities," Barnett wrote.
Gatto said he has not yet been contacted by investigators, and he mocked the complaint against him.
"College kids, owners of rental property and owners of mountain cabins should be very afraid, because the Republican chair knows where your legal residence is," he said.
He bought the Canyon Drive house in 2008 as an investment, renovated it and then rented it out after obtaining a certificate of occupancy from the city of Los Angeles in August 2009, he said.
A relative owns the mortgage lending firm that listed him as his agent, he said, adding that the relative listed the Canyon Drive address without Gatto's knowledge.
Regarding the campaign donations, Gatto said he has written campaign checks on accounts listing his business addresses, including those of his former law firms, in the past.
Demerjian said his office continues to look into a claim that Ramani did not live at the Burbank address he listed during the campaign. Ramani has said he was spending more than half his time in Burbank and intended to move permanently from La Cañada Flintridge if he won the Assembly seat.
Ramani said he has since been contacted by investigators.
"I've been told that this probably wouldn't be resolved until next year some time," he said. "I'm not concerned with it. They get these things all the time."