The Pennsylvania Supreme Court ruled today that Allegheny County must reassess its property values.

The unanimous decision on the cases of Clifton et al and Pierce et al v. Allegheny County -- argued before the court in September -- states that the base year method for property valuation, as applied in the county, violates the uniformity clause of the Pennsylvania Constitution. In 2005 County Executive Dan Onorato set property values at 2002 levels to avoid a tax hike on property owners with rising values.

Mr. Onorato said this afternoon that he doesn't believe the opinion necessarily requires the county to do a reassessment. He said there is "enough room" in the opinion to give the county several options, but he did not say what those options might be, and promised a full response within a week.

"I'm in my sixth year as county executive and we haven't done a reassessment yet," Mr. Onorato said. And he has no intention of doing one any time soon.

Writing for the majority, Chief Justice Ronald D. Castille stated that the system was unfair for property owners with stagnant or falling values. "[T]he Allegheny County scheme, which permits a single base year assessment to be used indefinitely, has resulted in significant disparities in the ratio of assessed value to current actual value in Allegheny County. The disparity is most often to the disadvantage of owners of properties in lower-value neighborhoods where property values often appreciate at a lower rate than in higher-value neighborhoods, if they appreciate at all."

The Supreme Court had some differences with Allegheny County Judge R. Stanton Wettick Jr.'s 2007 ruling that the base year method is unconstitutional on its face. The Supreme Court ruled that although the method violates the uniformity clause in this case, a yearly reassessment is not required. Judge Castille wrote: "It is only through the passage of time that a base year assessment will become stale, and thus unconstitutional."

The Supreme Court did not impose a firm date for when the reassessment must take place, leaving Judge Wettick to impose "a realistic timeframe."

Mr. Onorato said he was pleased the court upheld the constitutionality of a base-year system. But he conceded there is a problem with the county base-year ordinance because it doesn't set any time for conducting a reassessment.

Mr. Onorato said it's not clear whether he will be able to present a plan.

The new assessments could raise or lower the value of each property and the corresponding amount of tax.