Percentage of DNA tests with negative results
It is a fact that 20~30% of relationship DNA tests come out as negative, showing no biological relationship. However, this figure does not apply to all families, but rather is a figure obtained from families that had relationship testing done.
Many people still think of DNA tests are something from television or movies, but they have become surprisingly commonplace, and are very affordable at around only 20,000 yen for a test.
For families with suspicions about blood relationships that have DNA tests done there is a 20~30% chance of result coming back negative. However, if random families were submitted to DNA testing, the possibility of a negative result would likely be less than 0.5%.
If 20-30% of families chosen at random had negative results, it would mean that there 20-30% of couples were guilty of cheating, which would be a huge problem for society indeed.