Fairfax County Board Chairman John F. Herrity yesterday was charged with violating the Virginia public disclosure law last winter by failing to reveal his business relationship with a developer seeking the county's support for a major land rezoning.

Fairfax Commonwealth's Attorney Robert F. Horan Jr. said Herrity, a four-term Republican supervisor who has held the county's top elected post since 1975, will stand trial on the charge Aug. 21. Horan said the nonjury trial in Fairfax County General District Court probably will be completed in one day.

"The violation amounts to a willful failure to disclose," Horan, a Democrat, said after filing the charge. "He knew he was supposed to disclose, and he failed to do so. We will present evidence to show that."

Herrity, 54, issued a two-sentence statement yesterday saying that he did not violate the law. "I am deeply concerned over this matter, which is why I publicly raised it initially," he said in the statement. "However, I am confident of ultimate vindication in this matter." He declined to comment further.

The alleged violation, a criminal misdemeanor, is punishable by a maximum one-year jail term and a fine of $1,000. There is no provision under state law for Herrity's removal from office if he is convicted, Horan said.

Horan decided not to bring charges against Herrity involving cases in which he voted for rezoning applications without disclosing 1983 campaign contributions from the applicants. Also, Horan said he declined to charge other supervisors, whom he did not name, for failing to disclose their receipt of campaign funds from developers appearing before the board.

An arrest warrant containing the charge against Herrity was served on him by a county police officer about 2:30 p.m. yesterday during a recess in a meeting of the Board of Supervisors.

The charge centers on Herrity's participation in a controversial land use case in which Hersand Builders Inc., a Fairfax-based developer, was seeking county approval of a rezoning application that would allow a 137-unit town house development on a 41-acre tract in the Springfield district.

Herrity participated in the discussion and the vote on the proposed rezoning without disclosing that he had entered into a real estate venture with the president of Hersand, Herbert A. Aman III, and his wife Sandra, the company's sole stockholder, while the project was before the county board.

Herrity voted against the application, which was approved by the board 6 to 2, but he later supported a motion granting several waivers of county zoning standards.

Under state law, local officials are required to disclose a business or financial relationship with anyone involved in a land use case before participating in the discussion and vote in that case.

Herrity bought into the venture Dec. 18, when he made a $10,157 down payment for his one-quarter interest in an office condominium in Fairfax City. The Amans owned a 50 percent interest in the venture, which is valued at $195,000.

Herrity did not disclose his relationship with the Amans when the Hersand rezoning application came before the board at a public hearing on Jan. 27. Also, on Feb. 10, when the board approved the rezoning request, he failed to reveal that he was a business partner with the Amans.

In a letter to Horan that Herrity issued in May after being questioned by a reporter about the case, Herrity outlined a two-pronged defense. Herrity wrote that he did not disclose the relationship because the developer did not mention it in an affidavit filed with the rezoning application. Also, he said his vote against the rezoning request absolved him of any intent to mislead the public or the board.

Horan, however, said that neither argument would prevent Herrity's prosecution under the disclosure law. Horan said the burden to disclose a business or financial relationship between a developer and a county supervisor rests on the supervisor, not on the developer appearing before the county board.

The prosecutor added that the disclosure requirement exists regardless of whether the supervisor votes for or against an application filed by the official's business partner.

The Hersand application first came before the county board Nov. 18, when it was deferred for a week. It was postponed again on Nov. 25 and once again on Dec. 9 because of intense community opposition to the proposed town house development.

During that time, as well as during the period preceding the Jan. 27 public hearing and the Feb. 10 vote, Herrity played an active role in trying to defuse the public criticism. He discussed the project with residents during a town meeting in Springfield on Jan. 15.

And, according to Springfield residents protesting the rezoning, Herrity appeared briefly as they met with Supervisor Elaine N. McConnell (R-Springfield) just before the Jan. 27 public hearing. Some of the residents said that Herrity told McConnell, who was undecided about whether to support the project, that he would vote the way she preferred when the issue reached the board for a decision.

After voting against the main rezoning, Herrity and McConnell joined the rest of the board in unanimously approving several waivers exempting Hersand from county zoning standards.

Horan began his investigation two months ago after receiving Herrity's letter. Horan was assisted in the inquiry by a member of the county police department's investigative unit. He said the investigator questioned Herrity for the first time about a week ago, but Horan declined to comment on the nature of the discussion.

In deciding not to pursue the cases in which campaign donations were not disclosed before rezoning votes, Horan said, he examined "at least three" instances involving Herrity and a few cases involving other supervisors but found no evidence of an intentional violation.