Inconclusive cause is regarded as a topic with relevance in both civil and criminal law, with its application in areas where the perpetrator of the damage is unknown. Findings of this study, which have been conducted through the practical-analytical method of research, show that 4 views related to distribution of responsibility exist; First, neither is responsible since fault of no-one can be proven. Second, they have shares responsibility. Another view places the responsibility on the State, and the damages are payable via insurance funds or public funds (Bait-al-Maal). Based on the findings of another view, emphasises on balloting (lot), which was also accepted in the previous Islamic Penal Code of Iran. In French law, if the plaintiff has filed lawsuit against a group under the principle of error, the jurisprudence does not base the liability of each member of group, but takes into account their collective error. In Iranian Civil Liability Code, partaking in a group, a member of which has conducted an error result in shared responsibility for all members of that group.