The weighing of aggravating and mitigating factors is most often used in connection with the penalty phase of capital murder cases, when the jury is deciding the life or death of the defendant, but the same principle applies to many different cases, such as driving under the influence cases.
Aggravating Factors are any relevant circumstances, supported by the evidence presented during the trial, that makes the harshest penalty appropriate, in the judgment of the jurors.
Mitigating Factors are any evidence presented regarding the defendant's character or the circumstances of the crime, which would cause a juror to vote for a lesser sentence.
Each state has its own laws regarding how jurors are instructed to weigh aggravating and mitigating circumstances. In California, for example, these are the aggravating and mitigating factors a jury can consider:
- The circumstances of the crime and the existence of special circumstances.
- The presence or absence of violent criminal activity by the defendant.
- The presence or absence of any prior felony convictions.
- Whether the crime was committed while the defendant was under the influence of extreme mental or emotional disorder.
- Whether the victim was a participant in the defendant's homicidal conduct or consented to the killing.
- Whether the crime was committed under circumstances which the defendant reasonably believed to be a moral justification or extenuation for his conduct.
- Whether the defendant acted under extreme duress or under the substantial domination of another person.
- Whether at the time of the crime the capacity of the defendant to appreciate the criminality of his conduct or to conform his conduct to the requirements of the law was impaired as a result of mental disease or defect, or the affects of intoxication.
- The age of the defendant at the time of the crime.
- Whether the defendant was an accomplice to the crime and his participation was relatively minor.
- Any other circumstances which extenuates the gravity of the crime even though it is not a legal excuse for the crime.
The jury does not have to return an unanimous decision to recommend life in prison. If any one juror votes against the death penalty, the jury must return a recommendation for the lesser sentence.