Must a partner who kills another partner, knowing the latter already pardoned the killer for the homicide, face retaliation (Qisas)?

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Retaliation (Qisas) is obligatory upon the partner who kills his co-owner, despite knowing the co-owner had already pardoned the killer, regardless of whether a judge ruled on the pardon or not. This position is held by Abu Hanifa and Abu Thawr, and it appears to be the dominant view of Al-Shafi'i. The evidence for this is that the killer intentionally murdered a life deserving protection equivalent to his own, knowing he had no right to kill that person. Therefore, Qisas is incumbent, similar to a scenario where a judge ruled for a pardon. The existence of a scholarly dispute does not negate Qisas; for instance, if a Muslim kills an infidel, we execute the killer despite the dispute regarding his execution.