A friend and I were discussing something and the word criminal was used.  One thought is a criminal is one who has been convicted of a crime, however another thought was a criminal is one who has done unlawful things. 

That would mean a bank robber who wasn't convicted (yet) is a criminal without being caught or convicted.  I know that I've heard of the criminal element referring to some mob elements where many haven't been convicted of anything.

Which is it?  Do you have to be convicted of something to be a criminal or just be a law breaker?