Economic Expert’s Opinions on Property Valuation Admitted in Cook County Tax Sale Case
Posted on July 9, 2025 by Expert Witness Profiler
Cook County ran an annual property tax sale targeting homeowners behind on property taxes. When taxes went unpaid, the County obtained court orders to sell tax liens on delinquent properties. Private tax buyers then paid the outstanding taxes in exchange for collecting repayment, plus interest, from property owners. If the owners didn’t repay within about 30 months, buyers could petition for a tax deed and take ownership.
Michelle Kidd and Goyce H. Rates, two homeowners who lost their properties through this system, sued alongside two advocacy groups, Southwest Organizing Project (SWOP) and Palenque LSNA. They alleged the County’s tax sale process amounted to unconstitutional takings, excessive fines, and due process violations. Their homes, lost for debts under $10,000, were valued by the County between $166,000 and $389,000. Yet neither homeowner received compensation for the equity lost.
As part of the litigation, the Plaintiffs introduced Dr. William G. Hamm, an economist who supported the reliability of Cook County’s mass appraisal system to estimate market values. The Defendants countered with Ron DeVries, a real estate expert who challenged that approach. Both sides moved to exclude the other’s expert.
Economic Valuation Expert
William G. Hamm is a professional economist and a Managing Director of Berkeley Research Group, LLC (“BRG”), an expert services and economics consulting firm headquartered in Emeryville, California.
Hamm has a BA from Dartmouth College and a PhD in economics from the University of Michigan.
Real Estate Valuation Expert
Ron DeVries‘ valuation experience includes industrial, retail, office, hotel, multi-family (including FNMA/Freddie, HUD as well as LIHTC deals), and residential subdivisions for uses ranging from due diligence and financing to review appraisal.
DeVries is a frequent speaker at the Chicago Real Estate Council, the Chicagoland Apartment Association as well as private events for clients. He has testified as an expert witness in a variety of matters. DeVries is past national Chair of Education for the Appraisal Institute and previously served on the Appraisal Institute’s Board of Directors, and numerous committees.
Discussion by the Court
William G. Hamm (Plaintiffs’ Expert)
Qualifications
The Court found William G. Hamm qualified to testify. He is a professional economist and Managing Director at Berkeley Research Group with a PhD in economics. His experience includes building models to assess the market value of mortgage-related assets. Though not a licensed appraiser, the Court ruled that this does not disqualify him from evaluating Cook County’s mass appraisal system. His qualifications allow him to speak on complex modeling used to estimate real estate value.
Reliability
Hamm’s methodology involved analyzing how Cook County assesses property values using its Computer Assisted Mass Appraisal (CAMA) system. He reviewed public data, used certified Board of Review assessments, and calculated lost equity across a sample of properties. He acknowledged imperfections in the data and proposed interpolation to improve accuracy. The Court concluded that his methods were sound, especially given the lack of alternative sale data, and ruled that criticisms of his data sources go to weight, not admissibility.
Ron DeVries (Defendants’ Expert)
Qualifications
The Court found DeVries qualified as an expert. He is a licensed real estate appraiser with decades of experience in property valuation. While he lacks experience in mass appraisal modeling, he is qualified to critique how accurately Cook County’s assessments reflect market value based on his appraisal experience.
Reliability
DeVries relied largely on his own professional knowledge to evaluate weaknesses in the County’s system, such as infrequent assessments and a lack of individualized property inspections. Although his report lacked citations to specific county documents, the Court found this appropriate for the nature of his testimony. The Court held that any gaps in his review go to credibility, not admissibility.
Held
The Court denied the Defendants’ motion to exclude William G. Hamm, finding his economic expertise and valuation methods reliable and admissible.
The Court also denied the Plaintiffs’ motion to exclude Ron DeVries, holding his appraisal-based critique of Cook County’s assessments was qualified and relevant under Rule 702.
Key Takeaway:
The Court admitted both expert witnesses, ruling that Dr. William G. Hamm’s economic modeling and Ron DeVries’s appraisal-based critique were sufficiently qualified and reliable. Their testimony will play a central role in evaluating the constitutionality of Cook County’s tax sale system.
Case Details
| Case Caption: | Kidd v. Pappas |
| Docket Number: | 1:22cv7061 |
| Court Name: | United States District Court for the Northern District of Illinois, Eastern Division |
| Order Date: | July 07, 2025 |
