Short answer

In Texas an incarcerated person can generally execute a valid power of attorney so long as the document meets the statutory execution requirements: the principal must have capacity, the POA must be signed (or properly signed by mark), and the signature must be either acknowledged before a notary public or witnessed according to the statutes. For certain types of authority (for example, some health-care directives or real‑property transactions), additional execution or form requirements apply. See the Texas Estates Code rules that govern powers of attorney for full detail: https://statutes.capitol.texas.gov/Docs/ES/htm/ES.752.htm.

Detailed answer — formal requirements and practical steps (Texas)

1. Capacity of the principal

The principal (the person executing the POA) must have the mental capacity to understand what the document does at the time of signing. Capacity means the principal understands the nature and effect of giving another person authority to act on their behalf. If capacity is in doubt, consider getting a doctor’s written opinion before execution.

2. Signing and acknowledgement or witnesses

Under Texas law, a power of attorney is generally valid if the principal signs it and the signature is either:

• acknowledged before a notary public, or
• subscribed and sworn to before two adult witnesses (who must themselves sign as witnesses).

Because access to a notary can be limited in a correctional facility, the two-witness option is often used. Witnesses should be adults who are competent to testify about the signing and should not be named as the agent or a successor agent (avoid conflict of interest). For the statutory framework for execution requirements, see the Texas Estates Code chapter on powers of attorney: https://statutes.capitol.texas.gov/Docs/ES/htm/ES.752.htm.

3. Signature by mark and signing if the principal cannot physically sign

If the incarcerated principal cannot physically sign and instead makes a mark (e.g., an X or a thumbprint), Texas execution rules allow a mark only if the mark is made in the presence of the required notary or the required witnesses and the mark is acknowledged or witnessed according to the statute. The witnesses (or notary) should sign, print their names, and identify that they witnessed the principal’s mark. If possible, have an impartial prison official or health-care professional document that the mark was made by the principal.

4. Avoiding undue influence and proving voluntariness

The signing must be voluntary. If someone pressured the incarcerated person to sign, the POA may be invalid. To reduce risk of later challenge, arrange execution in a neutral setting, have independent witnesses, and document capacity and voluntariness (for example a medical note or a notarized statement). Banks and third parties often require additional proof that the principal signed freely.

5. Durable language and scope

To ensure the POA stays effective if the principal becomes mentally incapacitated, include clear “durable” language such as “This power of attorney shall not be affected by subsequent incapacity of the principal” or use the statutory durable POA wording. Also specify the powers you want to grant (banking, bill pay, property, health decisions if appropriate). Vague documents cause banks and other institutions to refuse authority.

6. Medical/advance directive differences

Health-care powers and advance directives may follow separate Texas rules (often in the Health and Safety Code). For example, certain health‑care directives may require two witnesses or a notary and contain additional language about life‑sustaining treatment; confirm those requirements before relying on a single form. See Texas Health & Safety Code chapter on advance directives for more detail: https://statutes.capitol.texas.gov/Docs/HS/htm/HS.166.htm.

7. Real estate and third-party acceptance

If the agent will handle real-property transfers, expect heavier scrutiny. Title companies and county recorders typically require a notarized POA that can be recorded. For real-estate matters, plan to have the instrument acknowledged by a notary so it can be recorded in the county where the property lies.

8. Practical realities in prison

• Contact the prison records or chaplain’s office to learn rules for notaries and witnesses; many Texas correctional facilities permit notary access by appointment or provide staff witnesses for certain documents.
• If the facility provides a notary, ask for a notarial certificate and official seal as part of the execution process.
• If a notary is unavailable, use the two-witness option and make sure witnesses meet statutory qualifications (not named agents/beneficiaries, adults, competent).
• Keep multiple original signed copies if allowed and send certified copies to banks, health providers, and the person chosen as agent.

9. What institutions will ask for

Banks, title companies, and health‑care providers may have their own POA acceptance forms or policies. They commonly expect a notarized POA, current identification for the agent, and sometimes a bank-specific affidavit of authenticity. If a bank rejects a POA executed inside a prison, ask the institution what additional proof it requires (notarization, affidavit, or court conservatorship in extreme cases).

10. When to consult an attorney

Get legal help when: the principal’s capacity is uncertain; the POA must handle complex real estate or business transactions; you anticipate a challenge for undue influence; or a bank refuses to accept a prison‑executed form. An attorney can prepare a document tailored to Texas law and the principal’s circumstances.

Helpful hints

• Ask the prison about rules for notary access and for who may serve as a witness.
• When possible, use notarization rather than relying solely on witnesses — notarization simplifies acceptance outside the prison.
• Choose witnesses who are neutral (not named as agents or beneficiaries) and who can later attest the signing was voluntary.
• Include clear durable language if you want the POA to survive subsequent incapacity.
• For real estate powers, plan to have the POA notarized and recorded in the county records office.
• Keep copies: give a copy to the appointed agent, a trusted family member, and the institutions the agent will contact (banks, utility companies, health providers).
• Document capacity: when in doubt, obtain a written note from a medical professional before signing.
• Verify institution requirements early (banks, title companies, and health systems may have specific forms or authentication steps).
• If the principal signs by mark, make sure witnesses or the notary clearly state that the mark was made by the principal in their presence.
• When in doubt, consult a Texas-licensed attorney to prepare or review the POA.