To participate in a lethal injection is to occupy the medical role and use medical training for a purpose that is not part of the goals of medicine and that harms the recipient of treatment.
Julian Savulescu's writing on conscientious objection is guided by an emphasis on the principle of distributive justice that does not allow religion to have a special status as justification.
If employees of religious institutions whose consciences conflict with those of their employers were to be granted legal protection for positive claims of conscience, the religious freedom of institutions within which they work would be gravely compromised.