How is DNA used to help solve crimes?
It can be used to identify people.
Blood and fingerprints both carry our DNA in them, which can be used to figure out who someone is. When they get fingerprints, one thing they can do is match it to a database to figure out whose fingerprint it is. The other option is to get a DNA sample from it and use that to track a suspect.
If you find blood on a crime scene, a DNA sample is easy to obtain. Whether identifying a suspect or victim, DNA can be used to identify them.
DNA tests are also used to rule out suspects. Police can take a DNA sample of a potential suspect, compare it to the DNA sample at the crime scene, and use the findings to either rule them out or confirm that they're the criminal.