Is handwritten trust amendment legal document?

What is the name of your state? Arizona

My mother recently died and had a living trust with my still living stepfather. She left me a handwritten note titled "Ammendment to living trust", instructing that on her death, her personal items such as jewelry were to be divided equally between my brother and me. First -- is this a legal document that carries any weight? Their "official" trust has everything going to my stepfather upon her death... her letter was intended to supersede the trust in this one area. If it is legal, how do I enforce it? My stepfather has her possessions and is aware of the letter but chooses to ignore it.

PS.. the handwritten letter is neither notarized nor witnessed. It merely is handwritten and signed/dated by my mother. It was sealed with instructions not to be opened until she had died.

Unfortunately it does not carry any legal weight. She should have consulted with a trust attorney to have the trust document officially changed/revised, or she could have/should have made the changes, signed by her initials, on a copy of the trust document, but she probably did not know that. You can consult with a local trust attorney to get a legal opinion about this and perhaps use it as a negotiating tool to try to see if your stepfather would be sympathetic enough to go ahead and honor her wishes.