This in and of itself very likely creates a bias against the defendant. For me, there is overwhelming evidence that many innocent people have been executed. To support the death penalty, you seem likely to either not believe in systemic injustice (which means you are also probably more likely to believe flimsy testimony) or accept that innocent lives are a tolerable tradeoff to ensure that some people are executed for their crimes. Both groups seem more likely to convict to me than a random sample.

Personally, I also feel that it is morally wrong to give jurors life and death decision making power. The jurors themselves can be deeply harmed by this if they later learn that they convicted a defendant on the basis of false evidence.

I think the bigger problem though is that the death penalty is too abstract. There are many people who believe that certain crimes are worthy of execution. I don't personally agree, but I accept other's beliefs on that point. But even if I grant the righteousness of execution in certain cases, it seems nearly impossible to implement justly and without heavy costs to society. This includes the costs to the people who must carry out the execution as well as the exceedingly high financial costs relative to other forms of punishment.

Of all the situations within which it would be morally okay to lie..