From an AP report:
Most of the 37 death penalty states shield execution team members' identities. Last month, Missouri lawmakers approved a bill that would allow members of execution teams to sue anyone—including news organizations—who discloses their identities. It hasn't been signed into law.
[Richard] Dieter, [head of the Death Penalty Information Center], said he believes protecting the identity of executioners helps anesthetize the public to what takes place in the death chamber.
Dieter's group, along with the ACLU, also thinks many incompetents are involved in lethal injection:
Death penalty opponents say Newton's May 24 lethal injection was the latest in a series of botched executions nationwide, and that executioners' identities and professional credentials should be open to public scrutiny.
They point to the case of Dr. Alan Doerhoff, a participant in Missouri executions who was revealed in news reports to have been sued for malpractice more than 20 times. The state is no longer using his services.
They also point to the December execution of Florida inmate Angel Diaz, who took 34 minutes—twice as long as usual—to die. Executioners administered a rare second dose of lethal chemicals to Diaz, and an autopsy found the needles had been pushed through Diaz's veins into the flesh of his arms.
Critics of both groups argue that they're really trying to ban the death penalty by other means: "They're setting up this Catch-22, saying only a doctor can do that, and knowing the doctor's association won't let them do it."