विबंध का सिद्धांत (Doctrine of Estoppel) क्या है?

While lodging an FIR for a suspicious loitering incident, a security guard's testimony states that he saw the suspect flee but did not directly witness the unlawful act. This constitutes which type of evidence?

A security guard relays second-hand information from a colleague about witnessing a break-in while lodging an FIR. This type of information is typically inadmissible in court under which category of evidence?