In the United States v. Cartwright case of 1972, the Supreme Court ruled on a matter concerning estate tax valuation. The issue at hand was whether or not an estate could be valued for federal tax purposes based on its fair market value at the time of death, as opposed to its potential future worth if sold under ideal conditions. This arose from a dispute over how much in taxes should have been paid by an estate that included shares in closely held corporations and partnerships which were difficult to sell due to restrictions placed upon them by state law and corporate agreements. The court unanimously decided in favor of the government's position that such assets should indeed be valued according to their actual worth at time of death rather than any speculative future value they might hold under different circumstances. It reasoned that this approach best aligned with existing laws governing federal taxation and provided greater certainty for taxpayers about what they owed.

In the dissenting opinion for United States v. Cartwright, Justice Blackmun argued that the majority's decision to allow a reduction in estate tax based on hypothetical selling costs was flawed. He contended that this approach opened up possibilities for manipulation and abuse of the tax system by allowing deductions based on conjectural expenses rather than actual ones. Furthermore, he pointed out inconsistencies in how such deductions were applied across different types of property within an estate, leading to potential unfairness and inequality. In his view, only real and necessary expenses incurred during administration should be deductible from gross estates before calculating taxes due.