"It has been narrated that Caliph, Ali ibn abi Talib {Radi'Allahu Anhu} in the Iraqi city of Kufa saw a Jew walking with his chain maille {armor}.
He said to the man "That armor is mine, I did not give it away nor sell it!
The Jewish man said: It is my chain maille and in my hands!" They went to the Islamic judge, Qadi Shourayh ibn al-Harith, where Ali, then leader of the Muslims {Amir al-Mu'minin} told the story to Shourayh. The Jewish man kept saying that it was his own.
The judge then told Ali: "Do you have any proof for your claim, Amir al-Mu'minin?" to which Ali brought his son, Imam Al-Hassan {Radi'Allahu Anhu} to the stand for his testimony.
But the judge rejected this and said the testimony of a son for his father is not accepted in Islam. Ali protested at first against this, but the Jewish man won the court case because the accuser could not bring forth any proof according to the Shariah.
Source: " Imam Jalal Ad-Din as-Suyuti, Tarikh al-Khulafa."
Note: Imam Ali accepted the ruling and the Jewish man was so impressed at the fairness of the judgement, that he said " I bear witness that there is no god except Allah and I bear witness that Muhammad