I am not sure about medium-risk public trust positions, but for high-risk public trust positions (think access to PII, social security # type stuff) they require an in depth personal history, including a meet and greet with an investigator (usually ex-law enforcement, so I was told).
Protip: Contractor or FTE, make sure you specifically ask HR whether or not there will be an additional screening, and whether or not it is a 'public-trust' position and what level that would be following your hiring.
I was pretty miffed when 'they' told me after the fact that my position required an additional background check and that my continued employment would be predicated on the outcome.
It shouldn't require a clearance unless you end up on a national security or defense project.
A valid prescription (the little white pads with a doctors signature, not a pot club membership card) for medical marijuana protects you from criminal prosecution, but not from employer drug testing programs. Executive Order 12564, signed in 1986, explicitly makes the federal government a zero tolerance drug free workplace.
It does not make it a "drug free" nor zero tolerance. It simply reinforces the arbitrary and capricious control doctors have over our bodies and mind. Under that order, it's fine to use meth (a schedule II medication), if you have a "valid" prescription, for abusive definitions of the word valid.
I worked for a different agency which required a Public Trust and the answer is yes.
For a basic public trust it was just a credit, background and drug test (the same treatment you would get at any employer who didn't trust their employees).
