If I understand correctly a gun liaison processes a firearm and accessories for dna and latent prints. I was under the impression it was more a function* of ATF than FBI(?)Means they are asking the FBI for help. Not joking.
The dna is held untill a direct sample/comparison can be made from the suspect or involved parties of that incident/crime. The samples from the firearm and or accessories are not compared to the combined dna index system(codis). It’s a direct comparison.