Often you are not granted a day in court. The poster who talks about California and it's high default rate on child support brings up a common theme. It is possible that he never knew about the court date. If not, I do not think that collecting so called child support from him is appropriate. Fine him for contempt.
At some point he will become aware of the Order against him, and have an opportunity to present his case to the judge. If someone like that came into court and convinced the judge he had not been properly served and wanted a DNA, the judges in my district would order the DNA, and continue (postpone) determination of past arrearages until the DNA results are in.