The prosecution made a significant error and dropped one of three counts against an immigration agent accused of accessing a confidential government database to help the 2006 campaign against now-Gov. Bill Ritter.

The count was dropped last week but the reason only became clear during testimony Monday.

Cory Voorhis is accused of accessing the National Crime Information Center database to obtain information on illegal immigrants who received plea deals when Ritter was Denver district attorney. According to testimony, he gave the results to the gubernatorial campaign of Bob Beauprez, which used it in an attack ad.

On Monday, an immigration agency investigator admitted under cross-examination that one person Voorhis is accused of looking up for political purposes actually was Voorhis' paid confidential informant in one of his office's biggest cases.

Omar Nunez provided information in the case against the Castorena family, who are accused of running a fake-ID ring for illegal immigrants.

Nunez's alias, Omar Perez, was on the list of 152 people that Ritter's office allowed to plea bargain to trespassing on farmland. A Beauprez ad implied that all were illegal immigrants, though only a few were proved to be.

Manuel Olmos, the internal affairs officer for Immigration and Customs Enforcement who investigated Voorhis, said he could not talk about Nunez because the information was sensitive.

But when U.S. District Court Judge John Kane ordered him to testify about the case, he said he did not learn that Nunez was a confidential informant for Voorhis until Sunday.

The defense then embarrassed Olmos by making him read a page in Nunez's file that stated he was a paid confidential informant for ICE. The document was signed by Voorhis, but Olmos had missed it.