The moment a child is born, the hospital staff kick things into high gear. They’re checking vital signs, running the Apgar test, clipping on those little wrist and ankle bands that tie them to their mother, and a hundred other things. 

They’re also in paperwork mode. They ink the baby’s foot and handprints, start the process of getting them a Social Security number, and perhaps most importantly, fill out the birth certificate that officially names them and certifies that they are a beautiful thing that exists in this wild and crazy world. 

Filling out this unassuming slip of paper is the most common way New Mexico fathers establish paternity. But paternity is more than just a name on a birth certificate. It influences custody rights, child support obligations, inheritance, determines who can make health care and other important decisions on behalf of the child, and may allow that child to access certain benefits like health insurance.

For families where parents are married at the time of birth, paternity is legally presumed. But for unmarried parents, same-sex couples, or in cases where paternity is uncertain, the law requires formal steps to establish paternity. These steps can be voluntary, such as signing an affidavit, or they can involve court orders and genetic testing.

If you have questions about New Mexico’s paternity laws, Attorney Bob Matteucci is ready to help you learn how paternity is established in our state, what legal rights and responsibilities come with it, and why it matters so much in custody and child support cases.

Why Paternity Matters in New Mexico

Paternity is about more than biology. It is a legal status that carries rights and responsibilities for both the parent and the child. Once paternity is established, it impacts:

  • Child Support — Children in New Mexico are entitled to financial support from both parents. A child’s mother will typically seek child support payments on his or her behalf. 
  • Access to Benefits — Social Security, veterans’ benefits, and health insurance may become available to the child depending on the father’s history, lifestyle, or job. 
  • Inheritance Rights — Legal children have an automatic legal right to inherit a portion of their father’s estate. This is true even in circumstances where paternity is established shortly after the father has passed away.
  • Access to Medical Information — A child can seek access to their father’s medical history, and a father can demand to be included in healthcare decisions made on their child’s behalf. 

Without legally established paternity, a child may lose access to these rights and benefits, and a father may have no enforceable role in the child’s life.

It is important to say here that just as paternity is about more than biology, fatherhood is about more than paternity. A man can be legally named a parent, but refuse to provide anything more than monetary support to their biological child. A man who steps up and provides the emotional support of a father to a child should never feel like they are less important to a child just because they are not legally that child’s parent. Paternity matters, but so does fatherhood. 

Establishing Paternity in New Mexico

There are several ways paternity can be established under New Mexico law. Which path is most appropriate depends on the parents’ attitude about parenthood and their marital status.

Presumption of Paternity

Under New Mexico state law § 40-11A-204, when a child is born to a married couple, the husband is legally presumed to be the father. 

This legal presumption also attaches to men who:

  • Divorced the mother of the child less than 300 days before the child’s birth.
  • Died or were declared medically invalid less than 300 days before the child’s birth.
  • Find out their marriage was invalid.
  • Married the child’s mother after the child was born and claimed he was the father, so long as:
    • He also filed a paternity form with the state (discussed more below) or 
    • He also agreed to be named on the child’s birth certificate or 
    • He made legally binding promise to support the child as his own or 
    • He and the child lived in the same household for the first two years of the child’s life, and he held himself out as the child’s father. 

This presumption can be challenged, but absent a dispute, no further steps are necessary.

Paternity by Affidavit

Unmarried parents may choose to establish paternity by signing a Voluntary Acknowledgment of Paternity (AOP). This affidavit can be signed at the hospital when the child’s birth certificate is getting filled out or later through the New Mexico Department of Health. Once signed and filed with the state, these documents have the same effect as a court order. 

If the mother is married to or recently divorced from someone other than the child’s biological father, the (ex)husband can seek a court order confirming he is not the child’s father. This may require genetic testing. 

Court Ordered Genetic Testing

When paternity is disputed, the court may order DNA testing. This testing must be done by a state-approved testing service. Results from over-the-counter tests or tests done through companies like 23andMe will not be recognized by the courts.

If the test confirms biological fatherhood, the court will issue an order establishing paternity.

Paternity and Unmarried Parents

Many paternity cases in New Mexico arise when parents are not married at the time of a child’s birth. Unlike children born into marriage, where paternity is presumed, unmarried parents must take extra steps to legally establish paternity.

If both parents agree on who the father is, Signing an Affidavit of Parentage is the simplest path forward. 

If there is disagreement over paternity, a court-ordered DNA test will likely be necessary. 

Whether everyone is in agreement or not, taking swift action to establish paternity ensures that both the child and the father are legally protected.

Paternity and Same-Sex Couples

In theory, New Mexico’s paternity laws apply the same way to same-sex couples as they do to hetrosexual couples. However, paternity (or “parentage”) disputes highlight the way LGBTQ people still have extra hoops to jump through to secure their rights. 

If a child is born into a same-sex marriage, New Mexico law presumes that both spouses are legal parents, even though the child is biologically related to just one parent.

If a same-sex couple is not married at the time of their child’s birth, the non-biological parent must take steps to assert their parenthood. This is typically done through adoption. 

Because family structures vary, same-sex couples often benefit from legal guidance to ensure both parents’ rights are secured, even if they do not expect to separate or divorce in the future.

When a Child Is Born to a Married or Recently Divorced Mother and the (Ex)Husband is Not the Child’s Biological Father

One of the most complex paternity scenarios arises when a child is born to a married woman, or a woman who has been divorced less than 300 days, and someone other than her (ex)husband is the child’s biological father.

As discussed above, New Mexico law presumes that the mother’s (ex)husband is the child’s legal father. Rebutting that presumption involves:

  • Going to court and having paternity proven through genetic testing, or 
  • Getting everyone involved to agree that the biological father will acknowledge paternity by filling out and filing a Voluntary Acknowledgment of Paternity (AOP) form.

Challenges to presumed paternity must be made in a timely fashion. When too much time has passed, courts are reluctant to sever the relationship between the child and the presumed parent, biology be damned. The courts consider what is in the best interests of the child in these situations. 

Paternity and Custody in New Mexico

Fathers who want to play an active role in their child’s life must establish paternity before they can seek visitation or exercise their decision-making rights.

Once paternity is established, both parents stand on equal legal ground. New Mexico law presumes that both parents should play a significant role in their child’s life. If a child’s parents cannot come to a custody agreement on their own, a court will decide what is in the child’s best interests. 

Paternity and Child Support

New Mexico law requires both parents to financially support their child. Once paternity is established, a father is expected to provide for his child. If he does not do so willingly, he can be ordered to pay child support.

Like many other states, New Mexico calculates child support payments via statutory guidelines. A child’s mother can ask the court to order the child’s father to pay support based on these guidelines. 

Serving Families with Dignity & Compassion 

Paternity is the foundation of a child’s legal relationship with their father—or, in some cases, their second parent. In New Mexico, paternity can be established by legal presumption, through voluntary acknowledgments, or by court-ordered genetic testing. Working with an experienced family law attorney ensures the process is handled correctly and with the child’s best interests at heart.

Attorney Bob Matteucci is a seasoned family law attorney who has worked with clients to prove and disprove paternity in a wide variety of situations. He works to get things settled quickly and discreetly without any Maury Povich-worthy drama. Please contact him today to schedule a meeting.