The blood of a child is recognized by its parents. It is the child’s blood and the adult’s blood if it can be dissolved in one piece, is the parents are born, otherwise it is not. It is understood that China’s Song Dynasty forensic writings recorded the ancient method of paternity determination. Then the blood drop recognition, reliable? This kind of blood recognition from the Three Kingdoms was created. In fact, there is no scientific basis. To put it bluntly, it is a pseudo-science that cheats people! Why is the blood drop not scientific? Because red blood cells have only a fragile cell membrane, no solid cell wall. Because of the osmotic pressure, red blood cells in water will absorb water and swell up, allowing the cell membrane to break into pieces. The antigen and antibody on the fragment can also be combined, but not like the intact cell membrane can be combined with a large number of antibodies, so it will not reach the weight required for precipitation, and will not produce small particles visible to the naked eye, so with this method, regardless of whether the blood type of the two drops of blood is the same, it appears to be fusion. So, blood recognition is bullshit. Then how can we identify relatives? By relying on modern medicine, DNA technology. DNA analysis for forensic physical evidence testing provides a scientific, reliable and rapid means to make physical evidence identification from individual exclusion transition to the level of the same can be identified, DNA testing can directly identify the crime, for homicide, rape and murder, broken body cases, rape and pregnancy cases and other major cases of difficult to provide an accurate and reliable basis for detection. With the development and application of DNA technology, the detection of DNA marker system will become an important means and way to solve cases. This method is already very mature as a paternity test and is internationally recognized as one of the best methods.