I built a prototype of a Private Set Intersetion using elliptic curve homomorphic encryption method for this very use case: The scenario goes 1) FBI indexes the dna using MASH algorithm (minhash like locality sensitive hashing of genomic sequences) of the person they are searching for. They then use homomorphic encryption and post this encrypted data online with a bounty for anyone to claim. 2)Now, individuals and corporations can try to claim the bounty; they also run MASH on their dna databases and encrypt each mash index using the same homomorphic strategy and submit it back to the FBI. 3)The FBI can now complete the private set intersection algorithm on the encrypted data and will only reveal information iff an assailants genealogy is found. The remaining sequences appear cryptographically random and thus protect the privacy of those persons.

I am currently working in blockchain space. If you want to know more feel free to message me.