Law, based on the precedent of older cases, is notoriously resistant to change, since the goal of maintaining the stability and predictability of the law holds back adaptation to new circumstances.  Perhaps the most vivid illustration of the tension between the need for continuity and the need to adapt to change can be found in the challenges of establishing - or legally changing - the paternity of a child in the State of New York.

Only a generation ago, establishing the paternity of a child born out of wedlock usually involved embarrassing testimony in court about sexual intercourse between the mother and the possible father.  Blood tests could only be performed when the child was at least six months old and they could only exclude (rule out) a particular individual as a possible father. Technology has advanced tremendously since then.  Instead of blood tests, which could only exclude, the current DNA testing can establish paternity with a high degree of accuracy.  DNA testing can be performed at any time and is much less invasive than the old-fashioned blood test. However, the law on establishing paternity has lagged behind the leaps and bounds of technology.

Children who are born to a married mother are legally presumed to be the children of her husband, and proving otherwise was and still is often an uphill battle.  When a child is born out of wedlock, the law in the State of New York favors identifying two legally responsible parents as soon as possible. Since it was not easy in the past to be certain of a child's parentage, public policy (and the best interests of children) generally favored establishing and keeping one individual as the father who is responsible for the child's support.  Legal fatherhood is far easier to create at the beginning of a child's life than it is to change later.

Section 516-A of the Family Court Act of the State of New York allows paternity of a child born out of wedlock to be established by a written acknowledgement of paternity at the hospital. This can be done with no DNA testing at all. If the admitted "father" does not petition within sixty days to vacate (set aside, nullify) his written acknowledgement, he has won an established status as the legal father of the child that he may regret later. After the sixty-day period has passed, the legal father who reconsiders must clear two hurdles. First, he must show "fraud, duress, or material mistake of fact" sufficient to nullify his original consent and acknowledgement of being the father, and then he must show that a change of legal fatherhood will not harm the interests of the child, under a legal doctrine called "collateral estoppel."

Collateral estoppel, also known as equitable estoppel, means that people can be stopped from doing things they would otherwise have the legal right to do (in this particular situation, changing the legal paternity of a child) because past events make it unfair or inequitable to allow them to proceed. The courts of the State of New York have favored keeping the originally identified father as the legal father, even when he finds out that he is not the biological father. The primary reason for this is to maintain as much security and stability for the child as is possible.

While the legal father, once established, has a tough fight to change his status, the key issue remains the best interest of the child. The collateral estoppel argument has been used to prevent a biological father from asserting his paternity rights when it would disrupt the child's existing relationship with an already established father-figure. The New York State Court of Appeals recently held, in Matter of Juanita A. v. Kenneth Mark N., that a man who was recently discovered by DNA testing to be the biological father of a twelve-year-old child could use the doctrine against the mother to block a paternity finding when the mother had already allowed the child to develop a father/child relationship with another man.

Mothers and possible fathers who wish to establish paternity in New York State now have a relatively easy do-it-yourself tool to walk them through this process. The Family Court Paternity Petition Program, set up by the New York State Office of Court Administration, allows parties who cannot afford attorneys to complete the necessary forms.

Both mothers and possible fathers should be cautioned to consider all the long-term consequences before asking for an order of filiation determining a particular individual to be a child's father. The status of legal father cannot be changed easily, and it can last for a child's lifetime.