Under what circumstances can police arrest a person in NSW?

In New South Wales, police have the authority to arrest a person if they have reasonable grounds to believe that the individual has committed a crime. This principle is rooted in the legal framework that ensures law enforcement can take necessary actions to maintain public safety and enforce the law. Reasonable belief does not require physical evidence at hand; rather, it is based on the information available to the police officer at the time, which could include witness statements, observations, or prior knowledge of misconduct.

In contrast to the other options, the criteria for arrest go beyond just having physical evidence or solely relying on witness reports. While a witness report might contribute to an officer’s belief that a crime has occurred, it is not sufficient by itself without reasonable grounds. Similarly, the decision can’t rest solely on a police officer's feelings; there needs to be a justified reason for the arrest. Hence, the correct option encapsulates the essential legal standard required for a police arrest in NSW.