On the face of it, convicting so many people in one death is preposterous. The fact that 16 of those charged were acquitted does not legitimize the process in the least. Only 123 defendants were in the courtroom; the rest were either released, out on bail or on the run.

It is impossible to know whether the court in the city of Minya where the verdicts were handed down was caught up in the animosity against Mr. Morsi and his supporters that has swept Egypt since his overthrow or whether the court was acting on directions from security officials. Either way, the case lays bare a prejudicial system that has been quick to punish Mr. Morsi’s supporters while ignoring gross human rights violations by the military-led government that replaced him.

Among these violations were the shooting of more than 1,000 Egyptians who protested the coup, and the subsequent arrest of thousands more. These incidents, in turn, triggered a backlash by Morsi supporters against police around the country. The backlash included violent protests in Minya last year, including the killing of the police officer that led to the trial.

Governments, of course, have a duty to protect their citizens and bring criminals to justice. But this trial had all the makings of a vendetta, not a fair and rigorous judgment. Even if the verdict is overturned on appeal, as lawyers predict, the process is illegitimate and perpetuates the government’s transparent effort to crush the Brotherhood. Mr. Morsi’s mistakes, authoritarian ways and efforts to monopolize power now seem almost modest compared with the official brutality of his successors.

The verdict should also raise alarms about the fate of other prisoners, including several journalists for the pan-Arab news channel Al Jazeera, whose trial is underway in Cairo, as well as 600 other defendants, whose mass trial is set to begin on Tuesday. The possibility that all could be faced with death sentences, a barbaric and indefensible punishment, is chilling.