Attorneys yesterday debated whether the owners of one property in Wilkinsburg can use the current market value of their property rather than the 2002 base year value for tax assessment purposes.

But when Judge R. Stanton Wettick Jr. makes his ruling, the decision could have a wide-ranging impact on the Allegheny County assessment system.

The property owners, James P. and Jennifer Daugherty, bought a house at 510 Todd St. for $31,500 in 2004. Because the county has decided to use the 2002 value of property as the base year, the couple's property is assessed at $66,900 for tax purposes.

Attorney Anthony Giglio, representing the couple, argued that the law allows taxpayers in communities with declining values to ask the county to use the current market value to set the assessed value. He called the option a "safety valve" to protect taxpayers.

Allegheny County Solicitor Michael Wojcik disagreed, saying that would lead to "chaos" in the assessment system. He said county Chief Executive Dan Onorato, who settled on the base year system last year after trying several other methods, has the discretion to set assessment policy and doesn't want to open the door to using the current market value.

The reason: If the court allows property owners to say their assessments are too high based on current market value, then taxing bodies could challenge assessments they consider too low in growing communities.

One reason Mr. Onorato went to the base year system was so that school districts could not ask the assessment board to raise the values of properties that sold for prices far higher than their assessments. In fact, the county has filed nearly 11,000 appeals on behalf of taxpayers who since 2002 had their assessments increased after school district appeals.

"We can tell the assessment board what our assessment process is," Mr. Wojcik said. "The only value that matters is the base year value."

Judge Wettick questioned whether the county can tell the assessment board what policy it should follow. He said the county would be "hard pressed" to defend a system without an option for taxpayers in declining communities.

"The base year is supposed to make sure [a taxpayer doesn't] pay more than his fair share," he said.

After the hearing, Mr. Wojcik charged that the Daughertys are a "straw client" challenging the system on behalf of school districts.

"This isn't about the Daughertys. It's about the school districts," he said. "That's what Dan Onorato is trying to put an end to. If we punish a property owner by increasing their tax bill solely because a sale occurred, that's wrong."

The base year system eliminates periodic assessments and "provides the stability we need" by treating all property owners the same, he said. Without the base year, he said, school districts use increasing property values to generate more revenue without increasing the tax rate.

Mr. Giglio wouldn't comment on the straw client contention, but said the sale price of the couple's property "shows they are living in a depressed area." He agreed that if he wins, the decision likely would allow school districts to challenge properties considered to be assessed too low, adding: "My answer to that is, so what?"

Judge Wettick didn't indicate when he would rule. If the county loses, Mr. Wojcik said, he immediately would appeal and seek an order to prevent anyone from using current market value until the appeal was heard.

The judge has another case scheduled for trial in December in which property owners are challenging the constitutionality of the base year system. The issue there is whether property owners are treated uniformly under the system.