Playing the devils advocate here but why keep convicts' DNA forever? Should ex convicts not have a right to privacy? I can imagine they might need some way to

Playing the devils advocate here but why keep convicts' DNA forever? Should ex convicts not have a right to privacy? I can imagine they might need some way to keep track of inventory in the prison system but once you've served the time, why keep the DNA? Just to make the cops' jobs easier? If there is a false positive on an ex convict's DNA, it still means we got the wrong guy.