A sample from evidence smaller than a dime is large enough to conduct a test, which will determine the makeup of the sample. A sample of blood or saliva is taken from the suspect. DNA from the two samples are compared to see if there is a match. DNA can remain in clothing for years, even after it has been dry cleaned. However, a thorough washing can make a sample untestable.
Cotton can retain some stains better than other fabrics.
If Lewinsky's dress was kept in a dry closet, the condition is good for DNA testing.