SAN DIEGO -- Prosecutors announced Friday they will not pursue four unresolved charges against a Chula Vista city councilman who was accused of lying to the county grand jury regarding his personal interest in an apartment complex that was being converted into condominiums.

Steve Castaneda was acquitted April 23 on six of 10 perjury counts, and prosecutor Patrick O'Toole said Friday that his office was dropping the case.

O'Toole's boss, District Attorney Bonnie Dumanis, issued a statement Friday afternoon following a hearing before Judge Michael Wellington, who dismissed the remaining counts.

"If a crime has been committed and we believe we can prove it beyond a reasonable doubt, we have a duty to file charges," she said. "I would like to thank the jury for its effort in trying to decide this difficult case.

"Given the not guilty on some counts and the impasse on others, today we asked the court to dismiss the remaining charges in the interest of justice. The District Attorney's Office will continue fulfilling its duty as a watchdog on behalf of the people."

From the time he was indicted last year, Castaneda maintained the charges against him were politically motivated. He alleged that Dumanis ordered the investigation as a favor to Chula Vista Mayor Cheryl Cox, whom Castaneda unsuccessfully challenged in the June 2006 mayoral primary.

The grand jury investigating Castaneda cleared the councilman of any wrongdoing in connection with his involvement with the Sunbow Villas, an apartment complex being converted to condominiums where his estranged wife was living.

During a June 2006 deposition, Castaneda said he didn't mention that he had met the project's developer, Ash Israni, because Israni didn't do anything for him with regard to the development.

Castaneda said he was renting an apartment at the complex for his wife and didn't plan on buying a condo there and didn't expect any benefits.

The councilman reiterated his testimony to the grand jury five months later.