Aggravating and Mitigating Factors Effect on Jurors in Capital Trials

Aggravating factors are elements of the crime or the defendant’s prior criminal record that not only make the defendant eligible for the death penalty but also serve to make the defendant more likely to receive the death penalty. Mitigating factors are elements of the crime or the defendant’s character and background that could make the defendant less likely to receive the death penalty. Statutes across the United States list many aggravating and mitigating factors that could be presented at trial. The existing research in psychology and law shows that jurors are sensitive to some factors but not to others. Experimental research has compared hypothetical cases in which various aggravating and mitigating factors are either present or absent. Other research, especially the Capital Jury Project, has surveyed or interviewed jurors who served in a death penalty case about what factors they considered important when making their decision.

Aggravating Factors

Jurors are more likely to sentence to death defendants who have committed a heinous, brutal, or cruel murder. Such crimes include those involving a single victim who suffers a lot of pain before death and also crimes with multiple victims. The brutality of a murder triggers jurors’ desire for retribution, or punishing someone for the harm that he or she has caused. Several lines of research show that jurors treat more severe crimes more harshly when assigning punishment in general, not just in death penalty cases. Jurors may not understand what the words heinous or atrocious mean, or they may believe that all murders are heinous. Thus, courts must instruct jurors that this aggravating factor is limited in some way, so that they are supposed to apply it only in cases involving torture, very serious physical abuse, or extreme depravity. However, even without such extreme case facts, jurors will sentence a defendant to death more often if the crime is more severe and causes more harm. Usually, in death penalty trials, a separate listed factor is included for murders with multiple victims, because heinousness is a specific legal term measuring how much suffering occurred before the victim’s death.

Jurors also consider the future dangerousness of a defendant—whether he or she is likely to commit another serious crime. In some states, jurors are specifically asked to decide whether the defendant is likely to re-offend, but even when not asked, jurors often bring this issue up during deliberations. The more the jurors fear that the defendant could re-offend, or even be released on parole, the more likely they are to sentence the defendant to death. Similarly, if the defendant has a prior criminal record that includes violent crimes, he or she will be seen as more dangerous, and jurors are more likely to sentence that defendant to death than defendants with no prior record.

Jurors are also affected by victim characteristics and victim impact statements. If the victim is a public figure or a policeman, jurors are more likely to sentence the defendant to death. The murder of such a person causes more harm to the community and deserves a more severe punishment. Furthermore, jurors are allowed to consider whether the victim was particularly vulnerable— for instance, because of young or old age or disability. Some research supports an increase in death verdicts in cases of child victims, but little research exists on other aspects of victim vulnerability. Jurors can also consider the effect that the murder has on the victim’s surviving family, friends, and the community. Several studies have found that jurors are more likely to give the death penalty when there is a large amount of suffering by the victim’s family and the community. Courts and researchers debate whether these effects are the result of jurors’ sensitivity to an increase in the amount of harm caused or instead an emotional reaction to the testimony.

Victim characteristics can be important even without victim impact statements. Some legal scholars and social scientists worry that jurors may be improperly considering the “worth” of the victim, or distinguishing between a good victim and a bad victim, which the law says they are not supposed to do. However, interviews with jurors suggest that jurors’ verdicts are different not necessarily because of a distinction between a good victim and a bad one but rather because of the similarity between the victim and themselves. Jurors can identify or empathize more with a normal victim chosen at random than a victim who is part of the crime or involved in a risky situation. In fact, that the victim is the defendant’s accomplice or otherwise part of the crime is often a mitigating factor. Overall, victim characteristics are weighed heavily a lot by jurors.

Many other aggravating factors exist in death penalty cases, such as committing the murder for financial gain, in the course of another felony, or after substantial planning. However, research has not yet addressed the effect of these aggravating factors on jurors’ decisions.

Mitigating Factors

Although jurors have trouble understanding the legal definition of mitigating factors, there are some factors that affect their decisions. The factors that have the largest effect are, generally speaking, those that are out of the defendant’s control, are more severe, and reduce the defendant’s responsibility for the murder.

Mental illness is the most powerful mitigating factor, even if it is not enough to make the defendant legally insane. Recognizing this large effect, the American Bar Association has recently called for the exclusion of severely mentally ill defendants from eligibility for the death penalty. Jurors likewise believe that a mental disorder can make a defendant less responsible for his or her crime. However, all mental disorders are not the same. Severe and typical disorders, such as schizophrenia and delusional disorders, will reduce the likelihood of a death sentence. Most studies also show that low IQ and “borderline” mental retardation also reduce death sentences, and defendants who are legally mentally retarded are not eligible for the death penalty at all. Disorders such as depression, antisocial personality disorder, or bipolar disorder have less effect on jurors, if any. Not much research has addressed these types of mental illness.

Researchers and courts recognize the fact that some mental disorders can be aggravating factors. The fact that a defendant has an antisocial personality disorder or a low IQ may cause jurors to think that that the defendant is dangerous, so jurors may be more likely to impose the death sentence. Specific symptoms that may influence jurors are the defendant’s inability to control violent impulses or to learn from mistakes. Not enough research currently exists to clarify when these disorders will be treated as aggravating and when they will be treated as mitigating.

Drug or alcohol addiction and intoxication are forms of mental disorder because drug use impairs the decision-making capacity of the defendant and can induce other disorders. In many states, voluntary intoxication cannot be used as a legal defense to a crime but can still be a mitigating factor. Two studies have shown that intoxication at the time of the crime can reduce the likelihood of the death penalty.

Having been abused as a child or having had a difficult childhood and background is also commonly presented as a mitigating factor, but again, this factor could produce mixed reactions in jurors. Very severe physical and verbal abuse reduces the likelihood of a death sentence, but less severe abuse or a troubled childhood may not affect verdicts. Some courts, legal scholars, and social scientists assert that a troubled childhood could also be seen as an aggravating factor if the defendant’s background includes violent acts or previous arrests. This again suggests that jurors are more concerned about a defendant’s dangerousness than about a defendant’s mitigating evidence.

Because jurors are concerned about the defendant’s dangerousness and likelihood to be violent, evidence that the defendant has been or will be a well-behaved and model prisoner can also reduce the likelihood of the death verdict. Only one (as yet unpublished) study has found this result, but this could be a very important mitigating factor. Likewise, the lack of a prior criminal record reduces jurors’ perceptions of dangerousness and, therefore, also decreases jurors’ likelihood of sentencing the defendant to death.

Interviews with jurors who have given a verdict of death penalty show that jurors will give the death penalty less often if the defendant expresses remorse for his or her crime. However, no experimental study has found an effect of remorse in death penalty trials. A defendant’s silence, or even a statement that he or she is not remorseful, could have an aggravating effect, producing more death penalty verdicts. A defendant’s remorse is often presented along with a religious plea, or testimony that the defendant has become more religious while in prison and is asking for forgiveness. At least one study suggests that a defendant’s conversion to religion can affect jurors and sensitize them to other mitigating factors as well.

Little research has addressed the effect of a defendant’s “good character,” such as serving the community, going to church, or previous good acts. Jurors may have difficulty considering this evidence if there are serious aggravating factors. Research shows that, during their deliberations, jurors focus much more on the crime than on the defendant’s character. Jurors also tend to focus on the circumstances that formed a defendant’s character rather than examples of previous good acts.

In the case of Roper v. Simmons in 2005, the Supreme Court banned the execution of defendants who committed their crime before the age of 18. Research conducted before that decision found that jurors did give the death penalty less often to juvenile offenders. Research also suggests that an 18- or 19-year-old defendant will be sentenced to death less often, but the mitigating effect of being a youthful defendant declines quickly beyond the age of 20.

Interviews with death penalty jurors have also found that jurors give the death penalty less often if there is any lingering or residual doubt about the defendant’s guilt, though in most cases, there is no such doubt. This type of evidence can be restricted in death penalty sentencing hearings, but jurors may carry over such doubt from the guilt phase of the trial.

See also:

  • Evaluation of Aggravating and Mitigating Circumstances in Capital Cases
  • Death Penalty
  • Juries and Judges’ Instructions
  • Jury Understanding of Judges’ Instructions in Capital Cases
  • Juvenile Death Penalty
  • Mental Illness and the Death Penalty
  • Mental Retardation and the Death Penalty


  1. Durham, A. M., Elrod, H. P., & Kinkade, P. T. (1996). Public support for the death penalty: Beyond Gallup. Justice Quarterly, 13, 705-736.
  2. Garvey, S. P. (1998). Aggravation and mitigation in capital cases: What do jurors think? Columbia Law Review, 98, 1538-1575.
  3. Roper v. Simmons, 543 U.S. 551 (2005).
  4. Sundby, S. E. (2003). The capital jury and empathy: The problem of worthy and unworthy victims. Cornell Law Review, 88, 343-381.