Im not sure if different strains would carry a different dna signature or not, but as far as beekeeper liability is concerned, I dont think it would be a real far stretch for an attorney to make on a civil suit. It wouldnt be a criminal suit where one would have to have a smoking gun fora conviction. A bee sting civil suit would be held to 'preponderance of the evidence' where dna probably wouldnt even come into play after a picture of the neighbors hives was produced. Let alone some good bearding pics or swarm in the neighbors apple tree. Not a frightful thing to beeks, but to a ticked off neighbor and a retained lawyer,they may speak volumes.
That's why it's important to meet or exceed local zoning restrictions in your bee yards. You have to show you've complied with existing ordinances along with showing you have taken sufficient precautions to reduce exposure to other people. That's why mine are enclosed within a 5 foot wire fence, signed (beware-Bee Hives), and located at least 50ft from the nearest property line.
Last line of defense is that you are providing a service (pollenation) directed by mother nature and that no one is liable for acts of nature such as getting Struck by lightening, drowning in a flood, falling off a cliff, or getting stung by a bee except the victim.