If that is the case punish the lawyer. But the lawyer's conduct should have no bearing whatsoever on the guilt or innocence or on the decision to execute the perp or to sentence him to life in prison.
It's time that criminal behavior was judged on its own and not discounted or excused because a police officer or attorney did something wrong.
How do you do that? The lawyer's conduct was geared towards muddling the decision over whether to execute or not. I agree that in an ideal world the lawyer's conduct should have no bearing upon this, but in reality lawyers are not always totally professional in their conduct and rules are made to discourage their treachery. In this case, the lawyer got caught and it may be the duty of the judge to throw out the case.
Without safeguards against corruption on the part of prosecutors, the ability of the innocent to defend themselves is significantly weakened. Should I ever find myself wrongly accused of a crime, I want all of the protections that I can get - even if it means that that terrorist murderers serve life in prison instead of getting the chair.
In any case, when the rules are established in advance, it's tough to fault anyone other than the participants when the system produces undesireable results.