the defendant was given what kind of stereotypes??

First, he was seen as someone with a prior record.

"Juror #10 stands stubborn in his belief that the boy is guilty. In a rant, he segregates the boy's "kind" (uneducated slum ridden folk) from the rest of society, describing "them" as "born liars". Quite rudely Juror #10 also attempts the argument that the boy is a "common ignorant slob" who "don't even speak good English," when he is in fact the ignorant one."

http://voices.yahoo.com/twelve-angry-men-analysis-7889442.html