In American TV shows, it appears that it is necessary to have blood tests before getting married. I've always wondered what these blood tests are for:
* at first I thought STIs
* then I thought genetic abnormalities
* now I'm thinking genetic diversity (ie to prove the couple aren't biologically syblings)
The other question is, are the blood tests simply an informative exercise (ie to ensure both parties know exactly what they are getting in to) or exclusionary (ie the wrong results could lead to refusal of a marriage licence).
And finally, I am guessing this doesn't apply in all states, because things like a spur of the moment, drive-through wedding (which I've also seen on American TV shows) wouldn't be possible if blood tests were required beforehand.