Of the characters introduced in act one of "The Crucible", select the character you feel would potentially be the most credible in a legal trial? The least credible witness in a legal trial?

In Act 2 of "The Crucible" the character of Mary seems to be the most credible one as she is the only one who has been with Proctor and has a good idea about his emotions. Tituba seems to be an incredible witness as she is believed to have the power to talk with the dead and says that even the devil has come to her.