A violation by a trustee of a duty the trustee owes to a beneficiary is a breach of trust. Section 456.10-1001.1 RSMo; Weldon Revocable Trust v. Weldon, 231 S.W.3d 158, 179 (Mo. Ct. App. 2007). Assuming a beneficiary is able to establish a breach of trust, the measure of damage is a different analysis.
Generally, a trustee is liable to the beneficiaries between whatever is higher between: (1) the amount required to restore the value of the trust property and trust distributions to what they would have been had the breach not occurred or (2) the profit the trustee made by reason of the breach. Section 456.10-1002, RSMo; Gould v. Gould, 280 S.W.3d 137, 142 (Mo. Ct. App. 2009) (“it is clear that co-trustees, as well as beneficiaries, have standing to bring a petition to remedy a breach of trust”).
Under prong (1), damages may include recovery of lost income, capital gain, or appreciation that would have resulted from proper administration. See Uniform Trust Code Commentary to Section 1002.