Hadith.3283 - And Ali ibn Asbat narrated from Muhammad ibn Al-Salt who said
I asked Abu Al-Hasan Al-Ridha (as) about a group of travelers who were ambushed by robbers on their journey. The robbers were captured, and some of them testified in favor of the others.
Imam (as) replied: "Their testimony is not accepted except if it is accompanied by a confession from the robbers themselves or testimony against them from others."