One kept a paperweight model of an electric chair on his desk. Another boasted about being named the “deadliest prosecutor in America” by the Guinness Book of World Records and mocked defendants with intellectual disabilities. A third was dragged from the courtroom when jurors who acquitted six defendants he had charged with shooting police officers said he approached them and reached for his gun.

These men are members of a very small club: five prosecutors who together are responsible for about one of every seven death-row inmates nationwide.

Even as most states have moved away from capital punishment, the practice continues to be used in a tiny fraction of counties, and under the leadership of specific prosecutors, according to a new report by the Fair Punishment Project at Harvard Law School.

The prosecutors are Joe Freeman Britt in North Carolina, Robert Macy in Oklahoma, Donnie Myers in South Carolina, Lynne Abraham in Philadelphia and Johnny Holmes in Texas. Of these five, only Mr. Myers remains in office. But during their tenures, each either secured dozens of death sentences personally or led offices that won hundreds. And each, in his or her way, embodies the vindictive, idiosyncratic nature of state-sanctioned killing.