Burden of proof seen as difficult.

Proving that certain buildings received low-ball assessments may be a slippery slope, says the president of the Appraisal Institute's New York City chapter. Her membership employs a two-prong methodology to quantify a building's value.

"In a nutshell, we use the sales transaction history of a building and the projected income, among other factors," says Ruth Agnese, adding that none of the indicted assessors were certified by the Appraisal Institute.

The Department of Finance may hire objective appraisers to determine the value of many city properties under scrutiny, believes Agnese.

She credits scientific and analytic methods as ensuring that AI members' conclusions are precise. But if one thing is apparent through, this scandal, this is a malleable science.

"Because of that it can be difficult to prove that an assessment was low-balled," she said.

One Manhattan real estate attorney identified a potential rift between the cause and effect.

"The cause is bribes and the effect is lower assessments. So how do you categorically prove, there was an effect? The assessment process is just so subjective," says Stephen Estroff, a partner at Jenkins & Gilchrist Parker Chapin.

Federal prosecutors claim that over the past four years alone the city has lost $160 million. Few published reports have examined this figure, and how it was derived.

Department of Finance commissioner Martha Stark did not return calls to elaborate on the sum.

With the investigation underway, details should emerge over the next few weeks to clarify the US attorney's stance. Until then, however many in the industry are questioning their figures, and the actual extent of the damage. It's clear that neither the city nor the real estate industry will emerge from this in a better light.

Steven Spinola, president of the Real Estate Board of New York, believes that the real damage isn't necessarily monetary.

"This really costs the city psychologically," says Spinola.

He admits that the city did lose some money, but he does not accept the $160 million sum at face value.

The Department of Finance is reportedly digging through years and years of property records in an effort to determine just how much the city lost. As this process continues more numbers are likely to surface.

"You must use data and facts to formulate an appraisal," says Agnese.

Licensing tax assessors would be one way to ensure that future assessments were ethical, believes Agnese. Unlike her membership, these officials were assigned large chunks of Manhattan real estate to assess. A licensed appraiser, however, evaluates one building at a time.

"It seems like the tax assessor system was very informal and cliquey," says Joe Dondiego, a managing director with Cushman & Wakefield's valuation services division.

"The process has to be more transparent, with more checks and balances," says Dondiego.

According to Dondiego, in other jurisdictions such as California owners aren't forced to wait years for the appeal process to be resolved. Dondiego also believes that a faster, more efficient process could lessen the demand to bribe someone to speed it up.