there’s know way that I know.

has it always been aggressive
if not then if it becomes very aggressive it probably is ,but sometimes it can be in pain of some sort
it doesn’t hurt to be bitten by a corn snake either so just try if it does bit doen’t throw it just gently put it back in the teranium
trust me i have 2 corn snakes and a green tree python i’ve been biten before

ps
don’t hold it if its about to shed it can irritate the new skin and hurt. this could cause it to bite( the skin gets pale and the eye cap dull)
check this place out for info
http://reptilechannel.com/
they have a very good magazine too

well u can try using a hook to see if he strikes at it first before holding him or u can just let him bite u since it most likely wont hurt but once u get use to him u can tell whens hes about to strike just by looking o ya and alot of pet snakes will no once ur holding him that your just gonna hold him and not hurt him if u handle him regularly