The case has all of the hallmarks of a crime story. Helmut Grasser slipped on the plastic gloves that were packed into the first-aid kit so he would not leave any fingerprints. He took two clean glasses out of the dishwasher, wiped them with a paper towel and then placed them on the table. He also placed a small spoon on the table and hoped his son would use it to eat his favorite dessert that was on the menu that evening.

And his 24-year-old son did indeed like the dessert. But when his son left, Grasser slipped on his gloves again and wrapped his son's glass and teaspoon in a paper towel. The next day, he sent the package of DNA samples off to be tested.

A few days later, he found a letter from the laboratory in his mailbox. He was nervous, paced up and down in his apartment, and eventually sat down in his favorite chair. The letter contained an invoice for Ђ489.40, a table full of numbers, two pages of text and a sentence in bold letters: "Paternity can therefore be ruled out."