Critical Thinking: Credibility Criteria

A source's ability to use any of the five senses to assess an event or situation.

• Sometimes called the ability to observe.
• Remember: this relates only to the credibility of an eye-witness to an event. Hearsay is not evidence.

It helps to ask the following questions:

• Did the witness see/hear the whole event? If not which part did the witness see or hear? What might they have missed?
• Does the witness have any medical condition or disability that could affect their ability to observe (and recall) the event accurately?
• Was the witness under emotional or other stress?
• Was the witness under the influence of alcohol or drugs? (Includes prescription medicine.)
• Was the witness distracted by other things that were going on at the same time?

Confirmation of, or support for, evidence given by one source by another source.

• Remember: corroboration confirms the reliability of evidence, unless there is reason to think that any of the sources may have reason to be untruthful or misleading.
• If accounts do not agree, or have conflicting evidence, they are contradictory.
• When the main parts of an account are corroborated but there is conflict in detail it is up to you to decide how important the details are.

When evidence or an argument contains two claims which cannot both be correct at the same time.

• Corroboration is for one or more people, consistency and inconsistency look for conflicts within one person's account of events.
• Remember: Do not confuse a counter-argument with inconsistency. Counter-arguments are intentional, and strengthen an argument. Inconsistency weakens it.

Tendency to be prejudiced against, or in favour of, certain beliefs, or people who engage in particular activities. 

This gives motive or subconscous reason to lie, misrepresent or distort information or evidence.

• Bias is a prejudice in favour of one side over another.
• It can be unconscious and unintentional.
• It may originate in religious or political beliefs, it can even be source from being a member of a group or family.
• A person who is biased may not have anything to gain from the outcome of the situation.

Being impartial; having no reason to favour either side in a dispute or difference of opinion.

• A neutral person should have no connection to any of the parties involved
• A witness who is neutral has no motive to lie or distort their account of events
• Many professions require neutrality, e.g: journalism and social workers.
• Remember: Bias is the counterpart of neutrality. Someone who is neutral has no reason to be biased.

Personal interest, usually financial, in a state of affairs or in an organisation leading to the expectation of personal gain from a favourable outcome.

• Provides a motive to say one thing instead of another - i.e: lie or distort.
• The difference between vested interest and bias is that the person with vested interest gains personally from the outcome of the situation.
  • Bias leads to a desire to believe one interpretation or explanation of events.
  • Vested interest provides an incentive to present one interpretation.
• Vested interest can be a motive to tell the truth.
  • For example, for a doctor lying would damage their professional reputation, so they have a vested interest in telling the truth.

Skills, experience and training that give someone specialist knowledge and judgement.

• Having expertise suggests someone is a reliable source 
• Courts of law often bring in experts, such as pathologists and forensic scientists.
• Relevant expertise strengthens the credibility of evidence.

What is generally said or believed about the character of a person or an organisation.

• We usually make decisions on whether to believe what someone tells us because of what we know that person has said in the past - this applies to critical thinking.
• Reputation may be based on what we know about someone's past performance, character or behaviour.
• It is not necessarily a reliable guide.