How does DNA analysis help identify or eliminate criminal suspects?

DNA fingerprint is very specific to an individual. You can pinpoint the individual person by DNA finger print. By collecting the semen from the victim of the rape, you can identify the criminal, very precisely. From very small sample of material from the nails of the victim, you can pin point the killer, by doing the DNA finger printing. By the same theory, you can eliminate the person, who has not done the crime.