Is the testimony of a son against his father admissible in cases of retaliation (Qisas) or prescribed punishment for slander (Hadd al-Qadhf)?

Primary text

The primary ruling dictates that a son's testimony against his father is accepted. The reasoning is that the son is not subject to the death penalty by the father's killing, nor is the prescribed punishment for slander applied to the father based on the son's testimony. The testimony is considered stronger in truthfulness because the son is suspected of acting in the father's favor but not suspected of testifying against him, similar to one's admission against himself.