The Supreme Court of Pennsylvania has held that the governmental privilege' to refrain from disclosing the identity of an informer does not limit the duty of the prosecution to make available the name and whereabouts of all material eyewitnesses to the defense.
Commonwealth v. Carter, 427 Pa. 53, 233 A.2d 284 (1967).
W. B. Pizzi II,
Criminal Law - Disclosure of Identity of Eyewitness Informer,
Duq. L. Rev.
Available at: https://dsc.duq.edu/dlr/vol6/iss2/12