William Taylor, former chief of the major-crimes unit at the Colorado U.S. attorney's office, was hired Monday to represent a federal agent accused of unlawfully helping Republican gubernatorial candidate Bob Beauprez's campaign.

Taylor, who specializes in government investigations at Denver law firm Holland & Hart LLP, is assisting Immigration Customs and Enforcement special agent Cory Voorhis, who is being criminally investigated by the FBI.

The agent allegedly used the National Crime Information Center database to search the name of an illegal immigrant featured in an attack ad aired by Beauprez's campaign.

Taylor will be joined by Holland & Hart partner J. Triplett Mackintosh, whose expertise includes customs law and white- collar defense. Mackintosh, on behalf of both lawyers, declined to comment further. Voorhis has also declined to comment.

The attack ad in question says Beauprez opponent Bill Ritter, when he was district attorney for Denver, reached a plea bargain with alleged heroin dealer Carlos Estrada Medina, an illegal immigrant who was freed and went on to commit a sex crime in California.

Although Medina's name does not appear on court documents in Denver or California, Beauprez's campaign said he was charged under aliases.

The Colorado Bureau of Investigation said last week Medina used the alias Walter Noel Ramo, the name of a man charged with heroin dealing in Denver in 2001 when Ritter was DA.

Ritter, a Democrat, alleged that the only way Beauprez's campaign could have linked the aliases was through the restricted NCIC database. Beauprez has said neither he nor his campaign has done anything wrong.