14-10407. Evidence of oral trust Except as required by a statute other than this chapter, a trust need not be evidenced by a trust instrument, but the creation of an oral trust shall be established only by clear and convincing evidence and the terms of the oral trust shall be established by a preponderance of the evidence. If a trust is created by written instrument, it may be amended or revoked only by written instrument executed by the settlor.
Arizona Legal Code