Death is the ultimate punishment a state can impose. Because of the death penalty’s severity and finality, its implementation should never be rushed or done without full due process of the law.

Yet Missouri will do exactly that if it proceeds with the execution of Mark Christeson on January 31. Intervention from the U.S. Supreme Court is now needed to prevent a grave miscarriage of justice. The federal courts have truncated due process by ordering unreasonably expedited briefing and hearing schedules, solely for the purpose of maintaining an execution date that was set at the State’s request while appeals were already pending. No court has ever fully considered the merits of Mr. Christeson’s important underlying constitutional claims, and no court has ever provided him with counsel free of conflicts of interest to raise those claims.

Mr. Christeson was 18 years old at the time of the offense for which he was sentenced to death and has significant cognitive limitations, scoring only 74 on an IQ test. There are also other mitigating factors in his case that were not properly presented at trial, such as a tragic history of pervasive sexual violence in his family. Yet no court has fully considered the merits of these claims or analyzed whether he has an intellectual disability that makes his execution unconstitutional, because the first attorneys to raise these claims filed the petition 117 days late. Although it is the lawyers who made the error, the fatal consequences of their mistake fall squarely on Mr. Christeson, and courts have declared that all of his claims for relief are now waived and “procedurally barred” from review. For many years afterward, Mr. Christeson’s lawyers concealed their serious error from their client, preventing him from seeking new counsel who could argue that the procedural bars should be set aside on equitable grounds.

These issues led the United States Supreme Court to intervene in 2014, granting a stay only hours before his execution. The high Court sent the case back to the lower courts, directing them to appoint new, conflict-free counsel.

Without even holding a hearing, and based on the limited evidence that counsel could compile with minimal funding, the court concluded that Mr. Christeson was not entitled to relief.

Responding to this directive, the federal trial court appointed new attorneys to represent Mr. Christeson, but it approved only 6% of their requested budget, thereby creating a new conflict of interest for substitute counsel who lacked the funding or resources necessary to adequately investigate and assess his severe cognitive impairments. Without even holding a hearing, and based on the limited evidence that counsel could compile with minimal funding, the court concluded that Mr. Christeson was not entitled to relief.

Before the federal Eighth Circuit Court of Appeals had decided whether to consider Mr. Christeson’s appeal of this decision, the state of Missouri decided to go forward with their plans to execute Mr. Christeson, setting his execution for January 31. After taking several extensions for filing their own briefs, lawyers for the State asked the court to set short deadlines for Mr. Christeson’s counsel so that the execution could proceed on schedule. Mystifyingly to many, the Eighth Circuit agreed to hear the appeal but then granted the State’s request for an expedited schedule, leaving Mr. Christeson’s attorneys a mere five business days over the holidays to file his appeal brief.

The Eighth Circuit ordered the district court to hold another hearing to develop evidence about prior counsel’s abandonment of Mr. Christeson. The lower court responded by scheduling the hearing less than two days after receiving the order. This timeline was so short that Mr. Christeson’s counsel could not even arrange for witnesses to travel to Missouri in time for the hearing, let alone adequately prepare to present evidence and make complex legal arguments. After the hearing concluded, the court ruled immediately from the bench, rejecting all of Mr. Christeson’s claims and sending the case along its hurried path toward execution.

If the death penalty is to be used at all, it should be carried out fairly and only with full due process of law. Justice should never be sacrificed for the sake of expediency in any criminal proceeding, and in a capital case, a court’s failure to take the necessary time to hear all relevant evidence is simply unacceptable.

No court has ever fully considered the merits of Mr. Christeson’s claims, and if this execution proceeds on January 31st no court ever will. Now is the time to halt the frenzied rush toward his execution and ensure that he is provided with the means and opportunity to present his case, before the state makes an irreversible mistake.

Carol S. Steiker is a professor at Harvard Law School and co-author with Jordan M. Steiker of “Courting Death: The Supreme Court and Capital Punishment.”