Quick answer

Yes. In Missouri you can challenge transfers made under a POA if you can show the principal (your grandfather) lacked the capacity to grant or authorize those transfers, or that the agent abused the authority (for example, by undue influence, fraud, or self-dealing). Challenges are typically brought in probate/circuit court. The sooner you act, the better, because third parties who relied on the POA in good faith may have defenses and assets can move out of reach.

Detailed answer — legal grounds and what courts look for

Common grounds to challenge transfers

• Lack of capacity: A POA is valid only if the principal had sufficient mental capacity when they signed it or when they authorized particular transactions. Capacity for a POA requires understanding the nature and consequences of the document and the transaction.
• Undue influence: If the agent or another person pressured, coerced, or isolated your grandfather into signing the POA or into approving certain transfers, a court can set aside those transfers.
• Fraud or forgery: If signatures were forged or the principal was misled about what they were signing, transfers can be voided and criminal charges may apply.
• Exceeding authority / breach of fiduciary duty: An agent must act in the principal’s best interest. Self-dealing or using funds for the agent’s personal benefit can be reversed by the court.

What evidence matters

Court decisions turn on evidence. Useful evidence includes:

• Medical records, neuropsychological testing, or physician opinions showing cognitive impairment at the time the POA was signed or transfers occurred.
• Testimony from witnesses present when the POA was signed (e.g., neighbors, aides, attorneys, bank employees).
• Bank statements, canceled checks, wire records, and transaction histories showing unusual or large transfers, repeated gifts, or rapid depletion of assets.
• Communications (emails, texts, letters) that show coercion, misrepresentation, or the agent’s intent to benefit personally.
• Comparisons to your grandfather’s prior financial behavior and estate plans (sudden, unexplained changes are suspicious).

Which court and legal standards

Challenges are usually filed in the circuit court (probate division) that handles guardianships, conservatorships, and estate matters. Missouri has enacted statutes addressing powers of attorney and the responsibilities of agents; see Missouri’s power of attorney statutes for guidance on agent authority and third‑party protections: RSMo Chapter 404 (Power of Attorney). For petitions seeking appointment of a guardian or conservator when a person may be incapacitated, see the probate/guardian statutes: RSMo Chapter 475 (Probate, Guardianship).

Third-party protections and practical limits

Missouri law gives some protection to third parties (banks, businesses) that act in good faith on a POA. That means undoing transfers can be harder if a bank accepted the POA and process in good faith. Prompt action improves your chance to freeze assets or obtain an accounting before funds are dispersed.

Remedies the court can order

• Void or rescind transfers found to be made while the principal lacked capacity or were procured by undue influence.
• Impose a constructive trust on assets improperly transferred to the agent or third parties.
• Order the agent to account for transactions and reimburse the estate for losses.
• Petition for appointment of a guardian or conservator if the principal is currently incapacitated and needs protection.
• Refer matters to prosecutors if there is possible criminal conduct (fraud, theft). See criminal theft statutes as a possible avenue: RSMo Chapter 570 (Crimes and Punishments).

Immediate steps to protect the estate

1. Preserve records. Obtain the POA document, bank and transaction records, and any correspondence about transfers.
2. Document observations. Write down dates, times, and witnesses who saw the signing or transfers and any changes in the principal’s memory or decision-making.
3. Contact the financial institutions. Ask whether they can freeze accounts or place holds while you consult an attorney. Be aware banks may refuse without a court order.
4. Seek emergency court relief. A petition asking for a temporary restraining order, temporary guardian/conservator, or an order to preserve assets can stop further transfers while the court evaluates the case.
5. Report suspected exploitation. Missouri’s Adult Abuse/Neglect authorities or local law enforcement can investigate if you suspect financial exploitation or criminal conduct.

When to hire an attorney and what type to look for

Contact an attorney experienced in elder law, probate, or fiduciary litigation as soon as possible. These attorneys know how to gather the right medical evidence, craft petitions to probate court, request temporary relief (asset freezes, emergency guardianship), and pursue recovery through civil claims or criminal referrals.

Practical timeline and considerations

There is no one-size-fits-all timeline. Some cases settle quickly after a demand and production of records. Others require months of litigation, medical evaluations, and forensic accounting. Acting quickly helps preserve evidence and increases the chance of recovery.

Helpful Hints

• Act quickly: the sooner you seek legal help, the easier it is to preserve assets and evidence.
• Get copies of the POA and all financial records before they are lost or destroyed.
• Gather medical records showing cognitive status near the time the POA was signed or transfers occurred.
• Look for red flags: sudden large gifts, transfers to the agent’s accounts, or a pattern of the agent isolating the principal from family and advisors.
• Ask banks whether they relied on the POA and whether they can provide transaction histories and surveillance (if relevant).
• Be prepared for contested proceedings—courts weigh evidence and consider good faith reliance by third parties.
• Consider both civil and criminal routes: banks and prosecutors may be able to assist when fraud or theft is suspected.
• Keep a contemporaneous log of actions you take and communications you have regarding the matter.