A more thorough explanation:

Reasonable belief

When there is a good reason to believe that a crime is happening or has already happened.

• A police officer sees someone breaking into a house and has a reasonable belief that a crime is being committed.
• A store owner notices a customer acting suspiciously and has a reasonable belief that they may be shoplifting.

These examples illustrate how a person can have a reasonable belief that a crime is happening or has happened based on their observations or evidence. In both cases, the individuals have a good reason to believe that a crime is occurring and can take appropriate action, such as calling the police or confronting the suspect.