The Supreme Court of Pennsylvania has rejected the long established, orthodox rule and embraced the modern rule which allows, as substantive evidence, the prior inconsistent statements of a non-party witness available for crossexamination.
Commonwealth v. Brady, 510 Pa. 123, 507 A.2d 66 (1986).
Joanna K. Budde,
Evidence - Prior Inconsistent Statement of a Non-Party Witness,
Duq. L. Rev.
Available at: https://dsc.duq.edu/dlr/vol26/iss1/9