That's the underlying message in a forthcoming study in the respectable journal Behavioral Sciences and the Law (subscription required). The abstract states:

The purpose of this study was to investigate the role of death qualification in venirepersons' evaluations of expert scientific testimony in capital trials. 200 venirepersons from the 12th Judicial Circuit in Bradenton, FL completed a booklet that contained the following: one question that measured their attitudes toward the death penalty; one question that categorized their death-qualification status; the Need for Cognition (NFC) scale (Cacioppo, Petty & Kao, 1984); a summary of the guilt phase of a capital case (which included the cross-examination of the state's expert witness); verdict preference; five questions concerning participants' evaluations of the expert's testimony; the penalty phase of a capital case; sentence preference; and standard demographic questions. Results indicated that death-qualified venirepersons were more likely to demonstrate a low need for cognition and view ambiguous expert scientific testimony as valid, important in their decision-making processes, unbiased, and of high quality. Finally, death-qualified participants were more conviction- and death- prone than their excludable counterparts. Surprisingly, death-qualified and excludable jurors did not differ with respect to whether or not they felt that the expert followed correct procedures. Legal implications and applications are discussed.

The erroneous and completely biased conclusion of the study states:

"Almost 20 years ago, the United States Supreme Court ruled the death qualification process to be constitutional (Lockhart v. McCree, 1986). However, psycholegal research continues to suggest otherwise. Given the court’s historical ambivalence with respect to the death penalty, a reversal of Lockhart is well within reach. It is only after the process of death qualification is declared unconstitutional that we will be able to move toward truly protecting capital defendant’s Sixth Amendment rights (Grigsby v. Mabry, 1985)".

What is more telling, however, is the "science" involved in this article. Briefly, the authors gave perspective venirepersons a simulated death penalty case, an attitude survey, a manufactured cross-examination transcript of the expert witness (but no direct or re-direct transcripts), and a measure known as the Need for Cognition Scale (NCS). The NCS has been around for a while and is in the public domain. The reader can decide how much weight to give this simplistic measure and whether it accords with the sweeping conclusions offer by the authors.