SAN DIEGO -- A Chula Vista city councilman lied to a county grand jury investigating his personal interest in a South Bay condominium conversion project, a prosecutor told jurors Wednesday, but a defense attorney said his client did nothing wrong.

Defense attorney Marc Carlos said Steve Castaneda never inquired about buying a condo at the Sunbow Villas complex and never made false statements to the grand jury about it.

Castaneda is charged with 12 counts of perjury and one count of mailing in a false document.

Deputy District Attorney Patrick O'Toole told jurors in his opening statement that Castaneda moved into the Sunbow apartment complex in 2005 when the Chula Vista City Council had already given tentative approval to convert the apartments to condominiums.

Castaneda gave a sworn deposition five months before testifying in front of the grand jury, the prosecutor said.

In that deposition, Castaneda said he was renting and didn't plan on buying a condo at Sunbow and didn't expect any benefits, the prosecutor told the jury.

The defendant reiterated that testimony to the grand jury, O'Toole said.

The prosecutor read an e-mail from a man associated with the owner of the complex, informing Castaneda when the conversion project would be completed and about the "pre-sale offerings."

Castaneda did not mention those discussions when he testified before the grand jury, the prosecutor said.

O'Toole accused the councilman of concealing the truth and impeding the investigation of the grand jury.

"You don't get to lie about it," the prosecutor said. "You don't get to obstruct a grand jury investigation."

But Carlos said everything Castaneda said under oath is true, and that he was never interested in buying a condo at Sunbow.

The attorney said the prosecution was trying to establish a relationship between Castaneda and the developer of the condo conversion project, Ash Israni.

Much of the case is based on assumptions people made when they heard Castaneda talk about wanting to buy two separate condos for him and his ex-wife because they had recently divorced, Carlos said.

Castaneda signed a short-term rental agreement for her to live at the Sunbow apartments, and he lived somewhere else, his attorney said.

"He wasn't treated specially. He wasn't living there," Carlos said of his client.

Castaneda's ex-wife filled out an online inquiry about the condo conversion project but really didn't like it there, Carlos told the jury.

Castaneda attended an open house for the conversion project, but went mostly for the doughnuts, the attorney said.

The grand jury cleared Castaneda of any wrongdoing in connection with the project, Carlos said.

"Mr. Castaneda actually did nothing wrong," the attorney said. "There's a big difference between interest and intent."

Castaneda, who will testify in his own defense, has called the charges politically motivated. He has alleged that San Diego County District Attorney Bonnie Dumanis ordered the investigation into his personal interest as a favor to Chula Vista Mayor Cheryl Cox, whom Castaneda unsuccessfully challenged in the June 2006 mayoral primary.

Castaneda, first elected in 2004, is running for re-election against three opponents.

His trial at the downtown courthouse is expected to last two weeks.