Answer:
Police matches the DNA with the criminal present in their database.
Step-by-step explanation:
Police use DNA that are collected at the site of crime in order to solve crimes because the criminals DNA are mostly found at the site of crime. the police collected these DNA and search in their database where the DNA of all the criminals are present. if the DNA matches with the criminal present at the database so it means that this criminal commit this crime so it is arrested and further investigation will be held. Yes, city police departments should make their own DNA databases in order to solve the case quickly.