In Enmund v. Florida (1982) 458 U.S. 782, and Tison v. Arizona (1987) 481 U.S. 137, the United States Supreme Court considered the mental state required for a felony-murder defendant, particularly an aider and abettor, to be eligible for the death penalty under the Eighth Amendment. The Court concluded there were at least three distinct mental states, two of which reflected the intent to kill, or the personal culpability necessary to permit the imposition of the death penalty. In both Enmund and Tison, the Court focused on the nature and extent of the defendant's involvement in the felony-murder as probative of mental state. Enmund v. Florida (1982) 458 U.S. 782, concerned a defendant whose participation in the underlying felony was minor. He drove his accomplices to the farmhouse of an elderly couple and parked on the side of the road, while his accomplices knocked on the front door of the farmhouse. When the husband opened the door, one accomplice grabbed him, held a gun to him and told the other accomplice to take his wallet. Alerted by the husband's cries for help, the wife appeared with a gun and shot one accomplice. One or both of the accomplices returned the fire, killing the couple. The accomplices then took the couple's money and fled to the car, where the defendant was waiting to drive them away. The defendant was convicted of first degree murder and sentenced to death. The Enmund Court reversed the sentence, observing the defendant was not on the scene of the killings, and his conduct was limited to driving the getaway car. The Court noted the killings were apparently spontaneous, precipitated by the wife's armed resistance to the robbery. The Court concluded because the defendant neither killed nor intended to kill, his mental state could not be equated with that of his accomplices, who actually killed, attempted to kill or intended to kill. (Enmund, at p. 798.) The Eighth Amendment does not permit the death penalty for a defendant "who aids and abets a felony in the course of which a murder is committed by others, but who does not himself or herself kill, attempt to kill, or intend that a killing take place or that lethal force will be employed." (Enmund, supra, 458 U.S. at p. 797.) Tison v. Arizona (1987) 481 U.S. 137 addressed a third mental state that falls between the polar opposites of the felony-murder defendants in Enmund, one which the Supreme Court characterized as "an intermediate" level of personal culpability. The defendants in Tison were two brothers convicted of first degree murder, whose involvement in the underlying felony was substantial, but who were found to have harbored no homicidal intent. As in Enmund, the Court examined the nature and extent of each brother's participation in the crimes as proof of his mental state at the time of the killing. The brothers helped their father and his former cellmate break out of prison, by smuggling in guns. (Tison, supra, at pp. 139-140.) The group brandished their weapons, locked up prison guards and visitors and fled. The tire on their getaway car went flat and one brother flagged down a passing car, while the others in the group hid on the side of the road. (Ibid.) Although the original plan was to steal the car, the father and the cellmate shot and killed the family of four who pulled over to help. (Id. at pp. 140-141.) The Tison Court determined the brothers' actions before, during and after the murders revealed that their "participation in the crime was anything but minor;" and also "supported a finding that they both subjectively appreciated that their acts were likely to result in the taking of innocent life." The Court went on to hold the Eighth Amendment does not prohibit the imposition of the death penalty in the case of the felony-murder defendant "whose participation in the underlying felony is major" and whose personal culpability is "one of reckless indifference to the value of human life." (Id. at p. 152.)