Detailed Answer

Short answer: Under New Mexico law, a power of attorney (POA) that is signed by an incarcerated person can be legally valid if it meets the state’s formal execution requirements: the principal must have legal capacity, the document must be signed by the principal (or in the principal’s presence by another person at the principal’s direction), the signature generally must be acknowledged or witnessed according to the statute, and the instrument should include clear durable language if it is meant to survive the principal’s later incapacity. For certain transactions (for example, transferring real estate) additional formalities such as notarization and recording of later documents also apply.

What New Mexico law requires (overview)

New Mexico has adopted statutory rules governing powers of attorney. These rules govern how a principal must execute the document, what language is required for durability, and how third parties should treat an agent acting under a POA. For the most reliable text of the statutes, see the New Mexico Legislature’s statutes on powers of attorney: New Mexico Statutes (search or browse for “power of attorney” or “Uniform Power of Attorney Act”).

Key formal elements that make a POA more likely to be accepted as valid

Capacity: The principal must have the mental capacity to understand what a power of attorney does when signing it. If capacity is in doubt, a contemporaneous written statement from a physician, psychologist, or other qualified professional can help.
Signature by the principal: The principal must sign the POA. If the principal cannot physically sign, many statutes allow another person to sign on the principal’s behalf, but that must be done in the principal’s presence and at the principal’s direction.
Acknowledgment or notarization: Many institutions (banks, land records offices) and many statutory schemes expect the principal’s signature to be acknowledged before a notary public. Notarization is the common way to establish that the signature is genuine. If a notary is not available in the correctional setting, the document is more likely to be challenged unless alternate witness or acknowledgment procedures recognized by state law are followed.
Witnesses (if required): Some statutes or situations require one or more impartial witnesses; others allow substitute procedures. Health-care powers of attorney or advance directives sometimes have stricter witness requirements. Verify which type of POA you are executing and follow the specific witness rules if they apply.
Durable language (if desired): To make the POA effective even after the principal becomes incapacitated, include clear durable wording (for example, language saying the agent’s authority continues despite later incapacity). If durable effect is intended but not stated, the POA may end if the principal later lacks capacity.
Prohibited witnesses/agents: Some settings restrict who can serve as a witness or as the agent (for example, a person who stands to benefit from the principal’s estate). Avoid using staff members who might be viewed by a court or third party as having a conflict of interest.

Special issues when a POA is signed in prison

Prison settings raise particular concerns you should address to improve the POA’s enforceability:

Availability of notary public: Many correctional facilities can arrange for a notary public or other official to witness or acknowledge an inmate’s signature. Ask facility staff about the procedure and get any notarial certificate attached to the POA.
Avoid conflicts of interest: Do not appoint staff who supervise or have authority over the inmate as the agent. Courts and third parties closely scrutinize documents where the agent may have exerted influence.
Independent witnesses: If notarization is not available, obtain impartial witnesses who are not named as agents or beneficiaries and who can later testify about voluntariness and capacity.
Document the circumstance of signing: Have the facility keep a record of the notary or witness, date and time, and any identity verification performed. If possible, get written statements from the notary or witnesses that the inmate appeared competent and signed voluntarily.
Institutional acceptance: Banks, government agencies, and title companies may have internal rules about accepting POAs executed in correctional settings. If the POA is intended for a particular institution, ask that institution in advance what they require (notary certificate, specific statutory language, or additional documentation).

Practical steps to maximize validity for POAs signed in prison

Request a notary or other authorized official from the correctional facility to perform an acknowledgment. A notarized POA is less likely to be rejected.
Include explicit durable language if you want the POA to remain effective upon future incapacity.
Choose an agent who is clearly independent of prison staff and who is not receiving direct financial benefit from the principal’s estate (unless explained and justified).
Obtain at least two impartial witnesses if the statute or institutional policy allows witness-based execution in place of notarization. Have witnesses describe the principal’s mental state and voluntariness in a signed statement when possible.
Ask a health-care professional to document capacity with a brief contemporaneous note if there is any risk of a later challenge.
Get certified copies of the executed POA for the agent and for institutions that will rely on it; consider recording agent-executed deeds or other real-estate instruments in the county records when transferring property.

Why POAs signed in prison can be challenged

Third parties and courts sometimes question POAs executed in correctional settings because of concerns about undue influence, insufficient capacity, or improper notarial procedure. Courts will closely examine the facts if a creditor, family member, or government agency disputes the agent’s authority.

Review the New Mexico statutory provisions that apply to powers of attorney for specifics on:

Execution formalities and required wording for durability
Whether a notary acknowledgment is expressly required for particular transactions
Special rules for health-care POAs and advance directives
Limits on who may serve as a witness or agent

For the current statutory text and details, consult the New Mexico Legislature website and search the statutes for “power of attorney” or the Uniform Power of Attorney Act: https://nmlegis.gov.

Helpful Hints

Ask the facility’s legal or records office about their notary/witness procedures before preparing the POA.
Use a standard statutory POA form that includes durable language and follows New Mexico’s model language when possible.
Attach a notarized or witnessed certificate showing identity verification steps taken at the time of signing.
If the POA will be used for real estate transactions, check county recording requirements and plan to have agent-executed deeds notarized and recorded later.
If family members disagree, consider having the principal sign a short capacity statement or have a medical professional document capacity at the time of signing.
Keep copies: the principal should retain a copy (if allowed), the agent should have an executed copy, and the agent should provide copies to banks or agencies that will rely on the POA.
When in doubt, consult a licensed New Mexico attorney about drafting and executing a POA in a correctional setting to minimize risk of later challenges.