Jury Understanding of Judges Instructions in Capital Cases

Research has shown that jurors in many types of cases frequently fail to understand the jury instructions they receive. However, this failure to understand has special implications in capital, or death penalty, cases. As in other cases, juror comprehension of instructions in death penalty cases is very low, and the difficulty of some of the terms and concepts used in the death penalty context exacerbates their confusion. But this misunderstanding carries with it an additional set of consequences in capital cases. Not only will jurors who misunderstand a judge’s instructions in a death penalty case have difficulty in applying the law accurately, but these jurors may also be more easily influenced by bias or prejudice in their decision-making process and may be more likely to vote for a sentence of death.

Guided Discretion

In 1972, in Furman v. Georgia, when the Supreme Court held that the death penalty was unconstitutional, it based its decision in part on the fact that the jury’s decision-making processes in capital cases at the time seemed “arbitrary” and “capricious.” When the Supreme Court approved new death penalty laws 4 years later, in Gregg v. Georgia and several other cases, it was because the Court felt that the new laws provided jurors with a framework intended to guide their decision-making process, guaranteeing that the jury’s discretion was controlled or channeled. Because this sort of guided discretion (communicated to the jury through jury instructions) was central to the

Court’s decision to bring back the death penalty in the United States, it is important that jurors in capital cases actually understand the jury instructions intended to provide that guidance.

Several components of death penalty cases make the jurors, the trials, and the jury instructions in those trials unique. During the jury selection process, for example, the death qualification process eliminates from service those potential jurors who have such strong views about the death penalty that those views might affect their ability to make an unbiased decision in an individual case. In addition, a capital trial is frequently divided into two phases: a “guilt phase,” in which jurors are asked to decide if the defendant is guilty or not guilty, followed by a “penalty phase” if the defendant was found guilty during the first phase. In the penalty phase, the same jurors are asked to decide whether a defendant should be sentenced to life in prison without the possibility of parole or to death.

Penalty Phase Instructions

A significant amount of research has focused on the jury instructions used in the penalty phase of capital trials. This research has focused on several concepts that are central to the penalty phase and the structure approved by the Supreme Court. First, the term aggravating circumstances is used in death penalty cases to describe the evidence that suggests that the defendant should receive a death sentence. This evidence is usually presented by the prosecution. Aggravating evidence includes those aspects about the crime or the defendant that, if true, should encourage jurors to vote for the death penalty. Aggravating factors are frequently limited to those listed in state statutes and can include things such as prior felony convictions or the circumstances of the crime in question. The term mitigating circumstances, on the other hand, describes the evidence to be considered by jurors that weighs in favor of a life sentence. Mitigating evidence is information about the crime, the defendant, or his or her life circumstances that, if true, should encourage a life sentence. Sometimes, specific examples of mitigation are included in jury instructions (e.g., the age or mental capacity of the defendant or social history), but mitigating evidence is not limited by law. The Supreme Court has said that jurors in death penalty cases should be able to consider any and all mitigating circumstances. As a result, death penalty statues frequently include a “catch all” category to let jurors know that mitigating evidence can include anything they believe should weigh in favor of a life sentence.

Both aggravating evidence and mitigating evidence are presented during the penalty phase of a capital trial, to inform the jury’s life and death decision. Although most jury instructions refer to these terms, many instructions do not provide definitions of the terms for jurors. Similarly, some states provide a list of “factors” that can be considered in the penalty phase but do not indicate whether the individual factors should be considered as aggravating or mitigating. In most jurisdictions, jurors are instructed to “weigh” aggravating and mitigating evidence in order to decide on the appropriate punishment. However, no specific formula for this weighing process or information about how it should take place is provided to jurors.

Juror Confusion

Evidence from mock jury studies, case studies, and interviews with actual jurors in death penalty cases shows that jurors have a great amount of trouble understanding these terms and applying the concepts. In some studies, jurors understood less than half the instructions they heard. This confusion extends beyond a failure to understand the words used; it also affects the ability of jurors to identify whether particular types of evidence should be used in favor of a life sentence or a death sentence and their ability to weigh the evidence presented in a legally appropriate manner. For example, studies have shown that many jurors believe that they are required to impose a sentence of death in certain situations, when in fact a death sentence is never required by law.

Many possible explanations for this confusion have been advanced. For example, some explanations focus on the use of confusing, passive language and the excessive use of jargon in the instructions. Others have suggested that jurors may become confused because they hold incorrect assumptions about crime and punishment at the time of the trial and these assumptions prevent them from understanding the accurate legal meanings of terms and instructions.

It is significant to note that in addition to the general lack of comprehension of instructions in the penalty phase of capital cases, the confusion does not seem to be evenly distributed, or to have a neutral impact. Although jurors have trouble with all these concepts, they seem to have more trouble understanding the concept of mitigating (the evidence that should be used in support of a life sentence) than aggravating circumstances. There are several possible explanations for this confusion. For example, in cases where the terms are not defined, jurors may rely on their personal knowledge of the terms. Because aggravating is a term we use more often than mitigating in our daily lives, it may be more familiar to jurors. No matter what the reason, this confusion means that sometimes jurors may not recognize mitigating evidence as being relevant to their decision. At other times, jurors may mistake mitigating evidence as being aggravating instead and use it against the defendant (to vote for death) rather than in his or her favor (by sparing the defendant’s life). This sort of error, a direct result of juror confusion, can have significant consequences for the accuracy of the decision-making process and for the defendant’s future.

Jury Decision Making

This lack of comprehension affects the jury decision-making process in capital cases in both direct and indirect ways. For example, as described above, research suggests that the skewed nature of the confusion may bias jurors toward death, rather than life, sentences, although the specific impact of juror comprehension on verdict choice is currently unclear. There is also some concern that this bias toward the death penalty embedded within the jury instructions works in combination with several other aspects of the capital-sentencing structure (including the use of two phases with the same jury for both and the death qualification process) to make death verdicts even more likely.

In addition to the direct impacts of juror confusion on verdict choice, research shows that jurors who are confused by the instructions will rely instead on the things they know and understand—if jurors do not understand the judge’s instructions, they are more likely to make their decisions based on their personal schemas and stereotypes. While a juror with a good understanding of the instructions is likely to base his or her decision on the relevant evidence and adhere to the weighing process in a legally appropriate way, the confused juror’s reliance on stereotypes allows for bias and prejudice to enter the decision-making process. Research has shown, for example, that mock jurors with lower comprehension levels are more likely to sentence a Black defendant to death than those with higher comprehension levels. In addition, mock jurors with lower comprehension levels find mitigating evidence to be more persuasive in the case of a White defendant than in the case of a Black defendant. Mock jurors with high comprehension levels do not exhibit the same discriminatory behaviors.

Finally, above and beyond the impact of low comprehension on juror verdict choices, it is clear that jurors—citizens who are being called away from their everyday lives and asked to make a very difficult decision—experience frustration with the instructions themselves, and many feel confused and upset during the decision-making process.

Improving Comprehension

Despite the limitations of the capital-sentencing instructions being used today, several studies have demonstrated that it is possible to improve comprehension levels using a variety of techniques. For example, several studies using psycholinguistic improvements designed to simplify and clarify the language in the penalty phase instructions have shown improved comprehension levels in jurors. Similarly, researchers have experimented with penalty phase instructions that incorporate case-specific details, instructions that include definitions of the terms aggravating and mitigating, enhancements designed to improve both the declarative and the procedural knowledge of jurors, and other innovations, all of which have been successful in improving jurors’ comprehension of penalty phase instructions to some degree.

Although there is a significant body of social scientific evidence documenting the limitations of juror comprehension in capital cases, and providing techniques and suggestions for improvement, juror comprehension of capital penalty phase instructions continues to represent an area of tension between psychology and the law. The Supreme Court has consistently upheld the death sentences of defendants challenging the instructions used in their trials, reasoning that there is a presumption that the jury both uses and understands the instructions provided in any case.


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  2. Furman v. Georgia, 408 U.S. 238 (1972).
  3. Gregg v. Georgia, 428 U.S. 153 (1976).
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