BOSTON — Two property assessors working on behalf of the town of West Tisbury lied to justify new valuations in an exclusive neighborhood of the town, resulting in land owned by William W. Graham being overvalued by $24 million dollars, the Massachusetts Appeals Court was told this week.

Counsel representing Mr. Graham, John Stevens, is seeking to have the court overturn a decision by the Massachusetts Appellate Tax Board last year, which upheld with only minor variation the assessors’ original valuation of Mr. Graham’s property.

He is seeking relief from land tax levied on his holdings, based on what he argues are inflated assessments.

The case deals with Mr. Graham’s assessments from fiscal years 2003 and 2004, when he paid more than half a million dollars in property taxes. Mr. Graham testified during the tax board hearing he believed he was owed more than $300,000 in relief.

Monday’s hearing was but the latest chapter in a long legal story, which had its beginning back in the property boom of the late 1990s. Within weeks of each other in 1999, two waterfront properties in the same neighborhood as Mr. Graham’s off Lambert’s Cove, sold for prices in excess of $10 million.

The first sale in July involved a parcel known as the Roberts parcel, of 81.4 acres, which went for $12 million. The following month saw a second sale, referred to in the court as the Ziff sale, in which 12 acres sold for $10.4 million.

When in 2002, the town was completing its triennial re-assessment of land tax values, these sales caused assessors to establish a new “neighborhood” for land tax purposes, neighborhood 200, including those two properties as well as Mr. Graham’s 235 acres, on seven lots.

Under the complex formula by which values are determined, a base rate is set, which is then ratcheted up according to various criteria. The so-called “multiplier” applied to the new neighborhood was set at 9.5, which resulted in the value placed on Mr. Graham’s land almost tripling.

The legalities are arcane, but the essence of Mr. Graham’s case is relatively simple: that the assessors based their new numbers on a single sale, the Ziff sale, then manipulated the criteria to make the Roberts sale fit them, and then discriminated against him by applying the formula inappropriately to large parts of his land his land even as they excluded other properties from the new neighborhood.

Testimony in the original case lasted 36 days over four months, making it the longest-running residential property tax appeal in the state’s history.

To date, Mr. Graham’s challenges have yielded little for him: only minor abatements on two of his seven parcels, lowering the total $51 million assessment by $520,000, meaning the town had to reimburse him $5,460.

But while the appellate tax board gave little financial relief, it lent credence to a central element of the Graham case: that during the 2002 townwide revaluation, assessors had wrongly altered a property record card for the Roberts parcel.

Prior to the 2002 revaluation, the card recorded the property as having water views. This was changed to say “no view”.

The two assessors testified they had visited the site and found the view obscured by trees. In fact, the appellate board found extensive views.

The board found testimony from the West Tisbury principal assessor, Jo-Anne Resendes and an employee of the town’s contracted valuation company, June Perry of Vision Appraisal, that the property had no view, was wrong. But that was not deemed to affect the value of the land.

The false testimony was deemed to have diminished the credibility of Ms. Resendes and Ms. Perry, not to have undermined the overall validity of the appraisal.

It was this evidence Mr. Stevens called a lie, both in his oral presentation to the appeals court this week and in his written brief to it.

“The assessments challenged in this appeal were based upon errors of law and justified by a factual statement the Appellate Tax Board found to be a lie,” he said in the brief.

“The assessors of West Tisbury created a valuation neighborhood based upon a single sale [the Ziff sale]; they extended that neighborhood beyond that single sale by manipulating the assessment of a neighboring property [the Roberts property]; and then hid their machinations behind the pretense that the backland of this neighboring property did not have an ocean view.”

Had the property record card remained as it was, the Roberts sale would have indicated a multiplier of 5.65, he said. So the assessors had to make it fit the new formula by altering the previous, accurate description of the land.

Furthermore, while all the Graham properties were included in the new neighborhood, others, which had previously always been in the same neighborhood, were excluded.

“In the end, the five Graham properties with no water frontage were not just the only non-conservation, non-waterfront properties placed in Neighborhood 200, they were the only such properties not to have their neighborhood multiplier reduced,” the brief said.

Mr. Stevens also stressed the inadequacy of the appellate tax board process in reaching its findings. He said it was unacceptable that its chairman, Anne Foley, who had the most detailed knowledge of the matter, had retired nine months before the decision. There was no evidence she had any role in writing the decision, he said, which stands in contrast with another case where a retiring commissioner had still been involved.

He concluded with the most precise statement to date of the amount by which Mr. Graham’s properties were allegedly over valued.

“The valuation of Mr. Graham’s property should be reduced by $24 million,” he said.

Counsel for the town assessors, Ellen Hutchinson, said there had been no “cooking of the books.” As part of the certification process, she said assessors had to reconcile sales prices with valuations.

“You can’t have a property that sells for $10 million assessed for $5 million,” she said.

The three justices hearing the appeal, Jospeh A. Grasso, Joseph A. Trainor, and Gabrielle R. Wolohojian, studied maps of the properties included in the new neighborhood 200, and their questioning was largely limited to queries about which properties were included or excluded and the reasons for that.

Asked by Justice Wolohojian about the factors which went into determining the assessment of values in a particular neighborhood, Ms. Hutchinson cited the similarity of housing stock, the property types and natural boundaries — in this case James Pond.

Subsequently there had been other high priced sales in the area. “You now have five sales which have exceeded $10 million,” Ms. Hutchinson said.

She denied that the new valuation had been based on a single sale, saying “the condition factor which became the basis for the valuation of the Graham property was derived from the Roberts sale.”