I received a CODIS hit letter and it says I need to use this to get a search warrant to collect a DNA sample from the listed individual. Why do I need another sample?

Offender samples used by the DNA Databank do not have an associated chain of custody and are generally inadmissible in court.  A new sample is needed to do a direct comparison between the individual listed in the CODIS hit letter and your case.  No statistical analysis can be performed without a known DNA sample.