Is the testimony of an interested party (خصم) accepted?
General Chapter
Al-Mughni
Book of Testimonies
Primary text
The testimony of an interested party is rejected in matters pertaining to that interest. This includes the testimony of an agent concerning the matter of his agency, a trustee concerning his trusteeship, a partner in the partnership matter, or an investor in the capital of the venture. For example, if someone usurps a deposited item from the custodian and then sues for it, their testimony is rejected because they are an interested claimant, akin to the owner.
Supporting text
The second type of interested party is an enemy (adūww), whose testimony is generally not accepted against their enemy, according to the majority of scholars, including Rabi'ah, Al-Thawri, Ishaq, Malik, and Al-Shafi'i. This enmity refers to worldly conflict, such as the testimony of one who was slandered against the slanderer, or the testimony of a victim of robbery against the robber, or the testimony of a victim's guardian against the killer. However, enmity based on religion, such as a Muslim testifying against a non-Muslim, or a person of Sunnah testifying against an innovator, does not invalidate testimony, as adherence to religion prevents bearing false witness.