When Jeff Sessions was Alabama’s attorney general, he supported the death sentence for a Ku Klux Klan member convicted of lynching a black teenager. Mr. Sessions, whose confirmation hearings for attorney general begin on Tuesday, points to this to rebut the charges of racism that have followed him for decades.

Yet we learn more about Mr. Sessions’ legal mind-set from a look at the 40-plus death sentences he fought to uphold as Alabama’s attorney general from 1995 to 1997. He worked to execute insane, mentally ill and intellectually disabled people, among others, who were convicted in trials riddled with instances of prosecutorial misconduct, racial discrimination and grossly inadequate defense lawyering. Mr. Sessions’ eager participation in an unjust Alabama capital system makes him a frightening prospective civil rights enforcer for the nation.

Mr. Sessions secured the execution of Varnall Weeks, who believed he was God and would “reign in heaven as a tortoise” after his death. After the Supreme Court banned executions of insane people, Mr. Sessions persuaded a federal court to defer to an Alabama court’s findings that Mr. Weeks was competent enough to be killed even though he met “the dictionary generic definition of insanity.”

Mr. Sessions also pushed for the death penalty for Samuel Ivery, a black man convicted of decapitating a black woman. At his trial, Mr. Ivery claimed insanity and presented evidence that he was a paranoid schizophrenic and believed himself a “ninja of God.” The prosecutor countered during closing arguments that “this is not another case of niggeritous,” that is, racism. Mr. Ivery later argued that the slur tainted his conviction with racial bias, but the appellate court sided with Mr. Sessions in upholding his death sentence.