An expert real estate appraiser hired by West Tisbury assessors last year estimated the total value of 235 acres owned by town resident William W. Graham at $64.5 million, significantly higher than the town's original assessments.

During four days of testimony in Boston last week, appraiser Kenneth J. Croft, whose experience on the Island includes work for the previous owners of Herring Creek Farm in Edgartown and Connecticut developer Corey Kupersmith, explained how he determined the value. Mr. Croft is set to retake the stand today in a prolonged legal hearing before the Massachusetts Appellate Tax Board, where Mr. Graham is challenging his property tax assessments for fiscal years 2003 and 2004. Mr. Graham's case rests on an argument that West Tisbury's system of land valuations and property tax assessments is fundamentally flawed.

Town assessors valued Mr. Graham's seven lots at Mohu off Lambert's Cove at just over $51 million in those two years, charging him more than a half million dollars in property taxes. Mr. Graham chose not to provide a private appraisal of his land during the tax board hearing, although he testified in July that he believes errors in the assessors' methods resulted in excessive valuations of roughly $30 million.

Mr. Croft, a staff appraiser for Coleman & Sons Appraisal Group in Wareham, testified at length about his nearly 100-page report that individually values each of the seven lots owned by Mr. Graham. He compared each of the lots to similar Island properties that sold within the last few years, and made adjustments to the sale prices to account for differences among the properties and the times that they sold.

Tax board chairman Anne Foley, who is presiding over the hearing, questioned Mr. Croft about certain relatively large and subjective adjustments he made among properties. In particular, she asked him about his comparison of Mr. Graham's 114-acre parcel with a distant view of Vineyard Sound to the 60-acre Polly Hill Arboretum property, purchased in 1997 for $2 million.

After making adjustments and comparing it to 10 other sales - many of them large conservation purchases by the Martha's Vineyard Land Bank or other nonprofit organizations - Mr. Croft valued the 114-acre Graham parcel at $15.4 million.

"Is there a point where the adjustments become so large it casts doubt on the comparability?" Chairman Foley asked Mr. Croft.

"The nature of real estate is that it's an imperfect commodity," he replied. "All properties are unique."

Mr. Croft testified about the overall Vineyard real estate market and knowledge he gleaned while conducting appraisals for other clients, including the Wallace brothers in Edgartown and Mr. Kupersmith, who tried for four years to build a private luxury golf course in the southern woodlands of Oak Bluffs.

The high-end Vineyard real estate market grew at a rate of roughly 40 per cent a year between 1997 and fall 2001, Mr. Croft explained, before it flattened out until January 2003. He said that the market is now increasing again at an annual rate of roughly 12 per cent.

"In my view, the market held its breath after Sept. 11," Mr. Croft testified last week. "It took a year-plus for things to start advancing again."

Mr. Croft said in his report and in his testimony that some of the largest real estate sales in the history of the Island are located near Mr. Graham's parcels on the north shore of West Tisbury around Paul's Point.

News surfaced on the Island last week of an $18.5 million purchase of two other neighboring properties totaling just under 10 acres. The purchase is linked to the family of publishing company heir Dirk Ziff, who with his brothers has participated in buying three other abutting waterfront lots for more than $10 million each.

Mr. Croft relied on the three previous Ziff purchases in his appraisal report and the assessors used them to determine other land values in the Paul's Point area. Attorneys for Mr. Graham have maintained that the sales should not set the neighborhood values because they are not representative of the overall market. The attorneys argued that the Ziffs are willing to pay more for the properties because they want to own contiguous lots.

Attorney Richard Wulsin, who is representing Mr. Graham, has not yet cross-examined the town's expert appraiser. But he raised a number of objections during Mr. Croft's testimony that challenge whether all the comparable sales used in the appraisal were handled correctly. Mr. Wulsin produced assessors' records from Edgartown that contradicted some of the factual information about sale properties listed in the appraisal report.

Chairman Foley overruled Mr. Wulsin's objections but asked that he raise the issues again during cross-examination. Chairman Foley also noted other inconsistencies and omissions she found in the report.

Mr. Croft valued a six-acre vacant hilltop lot with a panoramic view of Vineyard Sound owned by Mr. Graham at $5.5 million. He visited all of Mr. Graham's properties as part of his appraisal last summer, but Chairman Foley noted that his description of the hilltop parcel did not mention a 30,000-gallon cement cistern that sits on the lot. Mr. Croft told Chairman Foley that he was not aware of the cistern, but that he still had confidence in his appraisal.

Chairman Foley also asked Mr. Croft about potential access problems to a half-acre beach lot owned by Mr. Graham on the north shore. Mr. Croft valued the lot at $3 million and testified that he presumed it had deeded access.

"But if the presumption is wrong, would that affect the value?" Chairman Foley asked.

"Yes," Mr. Croft replied. "But to me it's unreasonable to assume a lack of access based on the circumstances."

Mr. Croft's testimony came one week after Chairman Foley ordered him off the stand to rewrite parts of his report.

When Mr. Croft first took the stand two weeks ago he significantly lowered his appraisal of Mr. Graham's 15-acre vacant interior lot to incorporate maps detailing wetlands on the property. After determining from the maps that an owner would have difficulty building on certain parts of the lot, Mr. Croft reduced his appraisal by 25 per cent - lowering it from $3.2 million to $2.4 million.

Town assessors also valued the land at $2.4 million.

Attorneys for Mr. Graham objected to the timing of the last-minute revisions. They argued town assessors failed to provide Mr. Croft with the wetlands maps until this June - more than a month after the tax board hearing began - even though Mr. Graham presented the maps to West Tisbury assessors more than two years ago.

Chairman Foley ordered Mr. Croft off the stand to rewrite the parts of his report relating to wetlands and to give Mr. Graham's attorneys enough time to review the revisions.

When Mr. Croft retook the stand last week, he noted that although the wetlands maps provided him with useful information about the properties, they did not affect any values other than that of the 15-acre lot. Wetlands have a much smaller impact on large properties, he testified.

"Wetlands are undevelopable land, so to that extent they are less valuable," Mr. Croft testified. "However, in the context of estate-sized lots, there's not necessarily a negative impact on value. To a certain extent they enhance the views."