CODIS is: computer technology (a database program and software), forensic science (DNA profiles rigorously measured and maintained), and telecommunications (the ability of local, state, and federal labs to share information and communicate electronically) all rolled into one.

CODIS is very powerful. Now a days it can do many things like:
...Establish both guilt and innocence;
...Link together seemingly unrelated cases (including serial crimes) so they can be investigated in tandem;
...Act as a set of "genetic fingerprints" that can positively identify not only criminals and terrorists, but also the remains of victims and missing persons, often years later;
...Keep dangerous felons behind bars by connecting them to other offenses;
...Quickly eliminate suspects and speed up investigations; and
...Bring closure and peace of mind to victims and their families by solving otherwise unsolvable crimes.

Simply put, CODIS stores DNA profiles from around the country in a series of local, state, and national databases, all linked via computers, enabling crime labs at every level to share and compare DNA profiles electronically. Lightning fast searches using CODIS can link DNA found at one crime to other crime scenes and to convicted criminals whose DNA is already on file.