A trustee owes a duty of loyalty to the beneficiaries and cannot place the trustee's own interests above those of the beneficiaries. Between loyalty and prudence, the duty of loyalty is more "fundamental" of the two.
It is said that two grand principles underlie much of the Anglo-American law of trusts: the trustee's duties of loyalty and of prudence.
The essence of a trustee's duty of impartiality is that the trustee may not favor one beneficiary over another, unless authorized to do so by the governing instrument.
A trustee is required to exercise reasonable care, skill, and caution in the effectuation of his duties and decision-making.