Does appointing a trustee for an elderly person revoke the elderly person's Will?

The short answer to this question is "no". Appointing a trustee for an adult whose capacity is diminishing and needs help with finances does not revoke the assisted person's existing Will. Since I was asked this question recently at a seminar but didn't get a chance to explain my reasons, I'll expand on that short answer here.

Perhaps the thinking behind the question was that a trustee is only appointed when an individual loses some or all of his or her mental abilities. While a person must have mental capacity to make the Will and sign it, there is no requirement that he or she must continue to have mental capacity up until the moment of death.

To me it wouldn't make sense that a Will be revoked by the appointment of a trustee due to decline of mental abilities. Once capacity is diminished, the individual cannot make a new Will to replace the old, revoked Will, Revocation on trusteeship would mean that every adult who had a trustee appointed would die intestate.

Perhaps the question arose because a trustee is appointed to take charge of all of the individual's assets, income, and debts. To some people this might suggest that the trustee has the final say on who gets what from the individual's estate. Keep in mind though that the authority given to a trustee by a court order (or Power of Attorney) ends the moment the assisted person dies. Therefore the Will doesn't come into play until the moment the trustee loses his or her authority. In fact, the trustee should actually be reading the assisted person's Will to make sure that the executor isn't doing anything to contradict it.