I think that to believe this, you have to believe (as Treehorn did before I explained the realities of how courts actually work to him) that the lawyer in question was idiotic enough not to realise that he hadn't actually asked whether or not Amanda smoked marijuana at that party. I think that unlikely.
It is far more likely, seeing as this is how cross-examination normally proceeds, that the lawyer was asking carefully-phrased questions to elicit exactly the answers he wanted. He didn't ask whether Amanda smoked marijuana at that party because he already knew, from reading the statements of Amanda, the boys downstairs, Rudy's friends and so forth, that she did not.
Lawyers and rationalists try to track exactly what was asked and exactly what was said. The untrained human mind is all too apt to fill in the blanks with whatever it thinks should go in there, which is in fact exactly the flaw in human cognition that questioning like this seeks to exploit.
Oh dear. SomeAlibi went down this dark path as well.
It does you and your cause no favours to post "Who cares if facts and logic show she is innocent? She's going to rot in jail because juries are stupid and courts are irrational! Ha ha!".