Can Jury Trial Innovations Improve Juror Understanding of DNA Evidence?
Dann, B. Michael, Hans, Valerie P., Kaye, David H., Judicature
A single spot of blood on a pink windowsill will tell investigators who broke a windowpane, turned a lock, and kidnapped 2-year-old Molly Evans from her bedroom in the middle of the night. An expert witness will testify that the DNA profile of the blood evidence recovered from the windowsill was entered into CODIS, an electronic database of DNA profiles.1 That process yielded a "hit," identifying the defendant as the most likely source of the blood inside Molly's room.
But will jurors be able to understand the expert's intricate analysis and use it to reach a verdict? And what-if any-steps can be taken to increase jurors' comprehension of complex DNA evidence?
Questions such as these prompted an NIJ-funded study on the impact of jury trial innovations upon mock jurors' understanding of contested mitochondrial DNA (mtDNA) evidence. (see "How mitochondrial DNA compares to nuclear DNA, page 153.") By examining how jurors in different experimental conditions performed on a Juror Comprehension Scale both before and after deliberations, researchers were able to assess whether four specific innovations improved jurors' understanding of this complex evidence and identify which innovations worked best.
The four innovations used in the experiment were:
* Juror note taking. Mock jurors were given a steno pad and pen for note taking and were told that their notes would be available to them during deliberations.
* Questions by jurors. Mock jurors could submit questions to the presiding judge, who obtained answers from an offsite DNA expert.
* Mitochondrial DNA (mtDNA) checklists. This innovation guided jurors through complex mtDNA evidence by asking them a series of questions. (see "mtDNA evidence checklist, page 154.")
* Multipurpose juror notebooks. Mock jurors were given notebooks containing paper, copies of the two experts' slides, the mtDNA checklist, a glossary of DNA terms used in the case, and a witness list.
Selecting the mock jury
Jurors were selected from jury-eligible adults called to jury duty in the Superior Court of New Castle County, Delaware. Jurors were randomly assigned to 60 eight-person juries. Each juror filled out an initial questionnaire that queried his or her views on the reliability of certain types of scientific testimony and about science in general. (see "Mock jurors' attitudes about science and DNA, page 156.") Researchers then assigned each jury one of the following conditions:2
The mock trial
The jurors then watched a videotape of an armed robbery trial. Prosecutors presented the testimony of bank employees who could not make a positive identification because the robber wore a blue hooded sweatshirt and a partial mask. However, the teller testified that she saw an unmistakable inch-long, horizontal scar on the suspect's cheek when he wiped his face with his gloved hand.
Police searched the crime scene immediately after the robbery and recovered a blue sweatshirt, a glove, and a small amount of cash, including some of the "bait money."3 Two human hairs recovered from the sweatshirt hood were analyzed and found to match the defendant's mtDNA. No other physical evidence was recovered.
Jurors learned that an anonymous caller told police the defendant had robbed the bank. Testimony established that the defendant owned a blue hooded sweatshirt, had a scar on his cheek, and had recently been seen flashing a large roll of cash. The defendant testified in his own defense and denied committing the robbery. He told a detective that he had never been in that bank and that he was at work when the robbery occurred. He claimed that the excess cash was from a friend's recent repayment of a loan.
In an attempt to dispute the prosecution's mtDNA evidence, the defense introduced evidence that the defendant's wayward halfbrother on his father's side lived in town at the time of die robbery. …