An Arizona sheriff facing a lawsuit by Latinos who claim they were racially profiled by his department is trying to revive the old controversy over President Barack Obama's birth certificate.

Maricopa County Sheriff Joe Arpaio said at a news conference Tuesday that investigators working for him have concluded the document is not legitimate. Arizona's Democratic Party immediately insisted Arpaio was trying to draw attention away from problems within his own agency.

A civil trial is set to begin Thursday in a lawsuit that accuses Arpaio's office of racially profiling Latinos. The suit is a precursor to a U.S. Justice Department lawsuit that alleges a broader range of civil rights violations against Arpaio's office.

So-called "birthers" maintain Obama is ineligible to be president because, they contend, he was born in Kenya. However, Hawaii officials have repeatedly verified Obama's citizenship, and courts have rebuffed lawsuits over the issue.

"President Obama was born in Honolulu, and his birth certificate is valid," Joshua A. Wisch, a special assistant to Hawaii's attorney general, said in a statement. "Regarding the latest allegations from a sheriff in Arizona, they are untrue, misinformed, and misconstrue Hawaii law."

Obama's campaign declined to comment.