A.R.S. § 6-383

Except as may be otherwise provided by law or by the writing creating the trust, a bank holding any asset as a fiduciary shall segregate all such assets from the general assets of the bank and shall maintain such safekeeping methods and records that the assets of each trust may be readily identified and distinguished from the assets of any other trust. Trust assets may be held in the name of nominees of the bank whether the bank is the sole fiduciary or acting with others, but the bank shall be responsible for the acts of any such nominee.