Interesting paper from Fauci in 2012:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3484390/
Putting aside the specter of bioterrorism for the moment, consider this hypothetical scenario: an important gain-of-function experiment involving a virus with serious pandemic potential is performed in a well-regulated, world-class laboratory by experienced investigators, but the information from the experiment is then used by another scientist who does not have the same training and facilities and is not subject to the same regulations. In an unlikely but conceivable turn of events, what if that scientist becomes infected with the virus, which leads to an outbreak and ultimately triggers a pandemic?