Kernrechtsfrage
Whether the tenant was denied the right to present witness evidence on an alleged remission of debt.
Extrahierter Entscheid
The lower court had to assist the unrepresented tenant under the social inquisitorial principle and could not reject the witness offer on formal grounds without guidance.
Extrahierte Begründung
In housing disputes, Art. 274d para. 3 CO imposes an ex officio duty to establish facts and to inform parties of their duty to cooperate. Once the tenant indicated a relevant witness, the judge had to either summon the witness or explain how to offer the testimony under cantonal procedure.