Paternity Blood Tests and DNA

A legal paternity test can have a significant impact. It can provide evidence for legal purposes in establishing child custody and child support.

Paternity tests scientifically establish the biological relationship between a father and child. Paternity can be determined by highly accurate tests conducted on tissue or blood samples of the father (or alleged father), mother, and child. These tests produce accurate results in the range of between 90 and 99 percent. They can exclude a person who is not the biological father and can also show the likelihood of paternity if they're not excluded. 

In a contested parentage case, court orders may require a party to submit to genetic tests at the request of any other party. If the father could be one of several men, the court may require each to take a genetic test to determine paternity. There are several ways to establish whether an alleged father is the natural and legal father of the minor child, such as the use of paternity blood tests and DNA paternity tests.

Paternity Blood Tests

Paternity blood tests were first performed in the middle half of the twentieth century by comparing blood types of tested parties. This involved the isolation and study of antigens appearing on red blood cells. Antigens are proteins or other substances sometimes present on the surface of red blood cells. Antigens can make a person's immune system react. Blood typing by antigen reaction allows healthcare providers to provide blood transfusions to patients in need of blood safely. Red blood cell (RBC) antigen testing also could rule out potential fathers in paternity disputes.

In the ABO blood typing system, humans can possess the A antigen (A blood type), the B antigen (B blood type), both the A and B antigen (AB blood type), or neither of these antigens (O blood type). Paternity blood testing can use RBC antigen systems because there are genes that code for the antigens. A child inherits these genes from their parents.

A mother with Type B blood and a father with Type O blood could not have a child with Type AB blood. The true father of the child must have the gene for the A antigen. Using RBC antigen systems for paternity blood testing did not provide for a very powerful test because the frequencies of the genes that coded for the antigens are not very low.

In the 1970s, a more powerful test was developed using white blood cell antigens or Human Leukocyte Antigens (HLA), resulting in a test that could exclude about 95 percent of falsely accused fathers. Several milliliters of blood are required to perform the test.

Blood types alone cannot determine who the father is, but they can determine the biological possibility of fatherhood.

DNA Paternity Tests

DNA (deoxyribonucleic acid) is the genetic material present in every cell of the human body. Except for identical multiples (such as twins or triplets), each individual's DNA is unique. A child receives half of their genetic markers (DNA) from the biological mother and half from the biological father. DNA testing compares the child's genetic characteristics to those of the mother. Characteristics not found in the mother must have been inherited from the father.

DNA paternity testing is the most accurate form of paternity testing possible. If DNA patterns between the child and the alleged father do not match on two or more DNA probes, then the alleged father can be ruled out. If the DNA patterns between the mother, child, and the alleged father match on every DNA probe, the likelihood of paternity is 99.9 percent. Today, child support agencies and courts regularly rely on DNA test results to establish paternity.

A DNA test can be performed by testing the blood or a cheek swab. A blood test uses Restriction Fragment Length Polymorphism (RFLP) to compare the father's and child's DNA. With a cheek swab (or buccal swab), the technician uses a cotton swab to collect cells inside the cheek to test for DNA. These tests provide a DNA sample for analysis. Children can get tested at any age.

Before getting a DNA paternity test, you need to consider the purpose of the test. If the parents seek a quick test to confirm what they believe, they may do a home DNA test. Home kits come with instructions for sample collection and can be easily found at drug stores and online. An at-home test is easy to take and can bring peace of mind.

If the parents want a test with results that will be court-admissible, then they need to make sure the lab is AABB accredited. An accredited lab has the highest standards for issues like chain of custody, DNA collection, and diagnostics.

What is a Non-Invasive Prenatal Paternity Test?

In the past, a fetal DNA test raised serious concerns. The CVS (Chorionic Villus Sampling) test and amniocentesis test carried risks to the fetus, including the possibility of miscarriage.

Today, a non-invasive prenatal paternity test can take place as early as the 7th week of pregnancy. It only requires a blood sample from the mother and a cheek swab from the possible father. The DNA profile of the developing fetus will appear in the mother's plasma. This permits the lab to analyze and compare the DNA of the fetus, the mother, and the possible father.

At What Point Do You Get a DNA Paternity Test?

It depends. When a child is born to an unmarried mother, the law designates her as the child's legal custodian. If she names the father and both sign an acknowledgment of paternity affidavit, this establishes legal paternity. If a married mother gives birth, the husband is legally presumed to be the child's father. If all parties are satisfied, a DNA test may never be needed.

Placing a father's name on a birth certificate is not dispositive of paternity. It does not tell us the biological father of the child. When a father signs an acknowledgment affidavit, his name will be added to the child's birth certificate. When a court finds paternity after DNA testing, it identifies the biological father. The court will direct an adjustment of the birth certificate to reflect the finding.

When there is uncertainty or a paternity dispute, parties may want to act quickly to pursue a DNA paternity test. State laws set different time limits on when a potential father must file a paternity lawsuit in court. A potential father who waits may never find out with certainty.

Need Help Establishing Paternity? Get in Touch With an Attorney

From paternity blood tests to DNA paternity tests, the science behind determining a child's father has advanced quite significantly over time. Consider whether you need a home paternity test or a legal DNA test for court. If you expect to file an action in court, be aware that there are certain legal procedures to follow to compel someone to submit to a paternity test. If you're interested in learning more about establishing paternity or using paternity test results in court, you can contact a family law attorney in your area.

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Can I Solve This on My Own or Do I Need an Attorney?

  • You can represent yourself in a paternity case, but establishing paternity can be emotionally and legally complex
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An attorney can explain the legal procedures and consequences of establishing paternity. Many attorneys offer free consultations.

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Don't Forget About Estate Planning

If you are in the midst of a paternity case, it may be an ideal time to create or change your estate planning forms. Take the time to add new beneficiaries to your will and name a guardian for any minor children. Consider creating a financial power of attorney so your agent can pay bills and provide for your children. A health care directive explains your health care decisions and takes the decision-making burden off your children when they become adults.

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