Is it permissible for either party to an incident to seek testimony from people who were present at the incident or not, for the purpose of self-defense, without the knowledge or permission of the other party, and by only hearing one side, knowing that the incident concerns only one of the parties and not those from whom testimony was requested?

It is permissible to request testimony from someone who can state the truth, even if the opponent is unaware of it. However, a witness is not permitted to testify except to what they know with certainty, based on Allah's saying: "Except for those who testify to the truth, and they know," and His saying: "And do not pursue that of which you have no knowledge."

Testimony is based on direct observation or hearing, depending on the nature of the matter being testified to:

1. Visual Observation: For matters for which testimony is not valid except through direct sight, such as theft, murder, and adultery. 2. Hearing and Observation: For contracts like sale and divorce. According to the Hanbalis, hearing is sufficient if the contracting parties are known with certainty. 3. Hearsay (Tasammu'): For matters whose knowledge is acquired through hearing widespread and frequently recurring news, such as lineage, ownership, and death. It is permissible to testify to these based on hearsay.