Troy Davis is scheduled to be executed on Wednesday for the 1989 killing of a police officer in Savannah, Ga. The Georgia pardon and parole board’s refusal to grant him clemency is appalling in light of developments after his conviction: reports about police misconduct, the recantation of testimony by a string of eyewitnesses and reports from other witnesses that another person had confessed to the crime.

This case has attracted worldwide attention, but it is, in essence, no different from other capital cases. Across the country, the legal process for the death penalty has shown itself to be discriminatory, unjust and incapable of being fixed. Just last week, the Supreme Court granted a stay of execution for Duane Buck, an African-American, hours before he was to die in Texas because a psychologist testified during his sentencing that Mr. Buck’s race increased the chances of future dangerousness. Case after case adds to the many reasons why the death penalty must be abolished.

The grievous errors in the Davis case were numerous, and many arose out of eyewitness identification. The Savannah police contaminated the memories of four witnesses by re-enacting the crime with them present so that their individual perceptions were turned into a group one. The police showed some of the witnesses Mr. Davis’s photograph even before the lineup. His lineup picture was set apart by a different background. The lineup was also administered by a police officer involved in the investigation, increasing the potential for influencing the witnesses.

In the decades since the Davis trial, science-based research has shown how unreliable and easily manipulated witness identification can be. Studies of the hundreds of felony cases overturned because of DNA evidence have found that misidentifications accounted for between 75 percent and 85 percent of the wrongful convictions. The Davis case offers egregious examples of this kind of error.