(S (S (NP (BASENP (NN Twelve) (NN percent)) (PP (IN of) (NP (BASENP (NN 1,043) (NNS prisoners)) (SBAR (WHNP (WP who)) (S (VP (VBD were) (VP (VP (VBN tested) (PP (IN for) (BASENP (NNS drugs)))) (PP (PP (IN from) (NP (BASENP (DT the) (NN start)) (PP (IN of) (BASENP (DT this) (NN year))))) (PP (IN until) (BASENP (NNP June))))))))))) (COMMA ,) (VP (VBD tested) (ADJP (JJ positive) (PP (IN for) (BASENP (NNS drugs)))))) (PERIOD .))