When a mother names you the father of her child in California, you should do everything possible to verify it is the truth. Being the legal father of a child means you become responsible for that child. This includes financial support. If you find out later that you are not really the father, you have little recourse. Sometimes, a mother will name someone even though she is not sure he is the father. According to Very Well Family, this is paternity fraud.
Most of the time, the mother knows you are not the father, but for whatever reason, she wants you to be. You may sign a legal paper stating you are the father. If you do that, there is not a requirement to have a DNA test. You may never take a test to scientifically prove paternity if you admit you are the father.
Paternity fraud may also occur if the state presumes you are the father because you were married to the mother when the child was born. The mother may even lead you to believe you are the father. Until you prove otherwise, you must meet all legal obligations that come with paternity.
Usually, the only way to prove paternity fraud occurred and to show you are not the father is by getting a DNA test. However, that is often tricky if the mother wants to continue claiming you are the child's dad. You may have to go through the court to get an order for testing. This information is for education and is not legal advice.