Read this and answer the question. If the question is unanswerable, say "unanswerable".

The United States Supreme Court in Penry v. Lynaugh and the United States Court of Appeals for the Fifth Circuit in Bigby v. Dretke have been clear in their decisions that jury instructions in death penalty cases that do not ask about mitigating factors regarding the defendant's mental health violate the defendant's Eighth Amendment rights, saying that the jury is to be instructed to consider mitigating factors when answering unrelated questions. This ruling suggests that specific explanations to the jury are necessary to weigh mitigating factors.

What sentencing factors did Bigby v. Dretke consider?
mitigating