Federal juries shy from death verdicts, 15 of 16 rejected last year. But state jury blood thirst still keen.

"It is just the opposite of the federal experience," Professor Baldus said, referring to the recent statistics.

Franklin E. Zimring, a law professor at the University of California at Berkeley, said recent results showed that federal defense lawyers were better financed and more competent than their state counterparts, particularly at presenting mitigating evidence in the penalty phase of the trial.

"It's almost a controlled experiment on the difference that quality of counsel makes," Professor Zimring said.