If you need further information in order to decide whether a witness is credible, then note down the further information which is relevant to deciding the question before you read on. Think of a...

If you need further information in order to decide whether a witness is credible, then note down the further information which is relevant to deciding the question before you read on.

Think of a couple of examples of people or ‘sources’ (like the BBC) you know and identify the areas in which they have a well-justified reputation for reliability and those in which they do not.