Wondering about studies on age and the application of the death penalty

After thinking hard about the great new Missouri study on prosecutorial discretion (details here) and exploring with my death penalty class various disparity issues (details here), I am wondering if there have been any serious empirical studies about the impact of age — both age of offender and age of victim — on the application of the death penalty.  Specifically, though there have been numerous empirical explorations of the impact of race (and a few studies on gender and geography), I cannot recall ever seeing a systematic examination of the impact of age on who does and does not get sentenced to death for intentional murder.

In all settings, age is an interesting (and debatable) sentencing variable.  One could contend, based on a variety of theoretical justifications, that age-of-victim and age-of-offender considerations are morally relevant in the application of the death penalty (and other sentencing regimes).  Of course, age of the offender has long been afforded constitutional significance: even before Roper, murderers under age 16 were not death-eligible; after Roper, murderers under age 18 are not death-eligible.  And I suspect that age of the victim has always had a practical impact: I would guess that prosecutors are more likely seek, and juries are more likely to endorse, the death penalty for those that kill kids and/or the elderly.

So, with that backdrop, I wonder if readers know of — and can point me to — any empirical studies addressing the impact of age in the modern application of the death penalty.   

UPDATE:  George in the comments helpfully points to this impressive 2000 study of Virginia's death penalty.  Table F.1 of that study suggests that prosecutors are more likely to seek the death penalty when there are juvenile victims; but tables C.1 and F.1 suggest that the gender status of the victim — i.e., that the victim is a woman — is a far more significant variable in prosecutorial decisions in potential capital cases.