Any party, including the party that called the witness, may attack the witness's credibility.
Utah. R. Evid. 607
Advisory Committee Note. The language of this rule has been amended as part of the restyling of the Evidence Rules to make them more easily understood and to make style and terminology consistent throughout the rules. These changes are intended to be stylistic only. There is no intent to change any result in any ruling on evidence admissibility. This rule is the federal rule, verbatim.