nothing... death is not a good punishment... its an easy way out... I think life in prison without parole is good punishment... then mold the punishment around the crime. for example... A man strangled my little nephew with the cording from a mattress. He put a pen in the cording and twisted until my nephew was dead... all because he was crying... I think a good punishment for him would me to have my nephews pictures (before death and autopsy photos) plastered on every inch of his cell. And then have a looped recording of the baby crying, the 911 call and the baby's older brother crying for him... repeated on a loop every second of his time... that way he couldnt ignore what he did no matter how much he wanted to... he would always think about it... and he would suffer.
Have a good one !