The answer is complicated. Some companies (i.e. GEDmatch) require its users to sign a consent form stating that their DNA could be used to help law enforcement efforts while others do not have that. Additionally, some companies use testing that requires a large clean sample of DNA and cannot work with mixed or small samples usually collected from crime scenes.
The answer is less about chain of custody and more about adjudication. Currently the matter rests with the individual laws of each state. California and Virginia are very pro-familial search while Maryland and DC completely banned it. Not sure where Indiana sits on this.
NOTE: I am still waiting to be verified so I guess MOO for the above. My verification is not as a lawyer however so perhaps one of them can jump in here.