What are the conditions for accepting derivative testimony (testimony about testimony)?
General Chapter
Al-Mughni
Book of Testimonies
Primary text
The first condition for accepting derivative testimony is that the testimony of the original witness must be impossible to obtain due to death, absence, illness, imprisonment, or fear of an authority or otherwise. This view is held by Malik, Abu Hanifa, and Al-Shafi'i. The justification for requiring the impossibility of hearing the original testimony is that if the judge can hear the original witnesses, they should rely on the certainty of their testimony rather than the mere probability concerning the derivative witnesses. Furthermore, the original testimony establishes the right itself, whereas the derivative testimony establishes the testimony about it, introducing a weakness involving two possibilities of error. Therefore, derivative testimony should only be accepted when the original witnesses are unavailable, similar to other substitutes.
Supporting text
A narration is transmitted from Al-Sha'bi that derivative testimony is not accepted unless the original witness has died, based on the reasoning that if both are alive, there is hope for their presence, making them equivalent to present witnesses. A similar view is attributed to Ahmad, though Al-Qadi interpreted it to include death and equivalent long absences.