Let There Be Doubt
Doubt or indecision at the start of an investigation is the hallmark of impartiality. A starting point that eliminates doubt has the hallmark of bias.
Seek the truth. Don't construct a case.
An imposed belief inhibits the asking of relevant and necessary questions.
Sir Richard Henriques, Justice of the High Court of England and Wales
Step 5 of the Five Steps to a Good Decision:
Check for Bias.