Robert Chambers, the infamous Preppy Killer who was busted last fall for dealing drugs to undercover cops, is going to use a "psychiatric 'poly-substance abuse' defense." His lawyer Valerie Van Leer-Greenberg told a judge, "He did not act knowingly" because he was so influenced by drugs. How influenced? Van Leer-Greenberg said, "He was using 10 to 12 bags of heroin a day," plus he smoked crack and pot and abused the painkiller Dilaudid. Currently at......