A good question. I have followed a number of cases with this in mind. It is that prosecuting authorities were caught like a deer in the headlights, with this great breakthrough in DNA.
All the defence initially had to do was to find a DNA that did not identify the accused. So far so good- indeed why not?
A case in Canada when a poor teen age girl was strangled. She was the clerk at an all night coffee shop in Winnipeg. A pair of gloves was found nearby. The defence set up a scream, saying "it was NOT his DNA". No indeed, a man was found not guilty after two trials and got over two million dollars compensation. I lost a brand new glove near a liquor store once. Never found it again. If the liquor store was hit and an employee murdered, my glove could have exonerated the perp. This using that logic.
We now know that if a factory operative sneezed over a garment, or quickly wiped their fingers on it, then packed it- DNA would be on the garment.
I am sorry for the Ramseys. That ransom note haunts me to this day. I cannot believe that an outsider wrote that note.