You’ll note that the lawyers on this thread had already pointed out that they cannot do “whatever possible to elicit feelings of doubt” - that they are limited to what the principles of evidence and canons of ethics allow.
On a related note, the Supreme Court in Nix v. Whiteside: http://caselaw.lp.findlaw.com/scripts/getcase.pl?court=US&vol=475&invol=157 rejected a defendant’s claim of inadequate assistance of counsel based on counsel’s insistence that the defendant not commit perjury during his trial, noting “Whatever the scope of a constitutional right to testify, it is elementary that such a right does not extend to testifying falsely.”
I’ve not heard of a lawyer facing disbarment for suggesting that a jury can ignore the law, but then, I’ve not heard of a case since Morgentaler where a defence counsel made that suggestion.
When a defendant testifies under oath that he did not commit the crime for which he is being charged, and the jury subsequently finds him guilty, could he be charged with perjury? Or does one have an absolute right to lie, where the plain fact of the crime is concerned. (Otherwise, presumably, a defense would be practically impossible if a guilty person was barred from claiming innocence).
The defendant is not required to take the stand. If he does he is subject to cross-examination and required to comply with the jurisdiction’s perjury laws.