In the 1989 case Davis et ux. v. United States, the Supreme Court ruled on whether a taxpayer could deduct interest paid on an overpayment of federal income tax for state income tax purposes. The taxpayers had made an overpayment to the Internal Revenue Service (IRS) and sought to deduct this amount from their state taxes in California. However, both the IRS and lower courts denied this deduction because it was not considered "interest." The Supreme Court affirmed these decisions, ruling that under Section 163 of the Internal Revenue Code, only amounts classified as "interest" can be deducted for state income tax purposes; since overpayments are not categorized as such by law or by IRS regulations, they cannot be deducted. This decision clarified how deductions should be handled when there is an overlap between federal and state taxation systems.

In the dissenting opinion for Davis et ux. v. United States, Justice Blackmun argued that the majority's decision to allow evidence obtained in violation of a suspect's Miranda rights was fundamentally flawed and undermined the principles established by Miranda v. Arizona (1966). He contended that allowing such evidence would encourage law enforcement officers to ignore or circumvent suspects' constitutional rights during interrogations, leading to potential abuses of power and miscarriages of justice. Furthermore, he disagreed with the majority’s view that a suspect must explicitly invoke their right to remain silent for it not be waived; instead, he believed any waiver should be clear and unequivocal before being accepted as valid. Finally, Justice Blackmun criticized the majority for failing to consider how its ruling might affect public trust in law enforcement agencies and judicial processes.