Correct me if I am wrong, but there are actually sentencing hearings, one of those places that Judges and District Attorney's (Crown Prosecuters) make decisions. The "crown" does not always go for the death penalty in all murder cases, that is why we assign different degrees of murder. The system could be revamped if it was already being changed, to include the death penalty, such as in the case of my home and native land, to include clauses to permit the death penalty, quickly and immediately, in the case of 100% absolute guilt, such as the aforementioned Paul Bernardo case.
As for the second statement you made, no she did not kill a cop, but truly, though a cop killing may shock, outrage, and get twice the press of any other murder, and though for us in EMS it may hit closer to home (I knew and had worked next to Doug, the fallen RCMP officer) is one life worth more than another? This girl, in pre-meditated and horrifying fashion, killed her entire family, she should be a poster child for changes to young offender laws and death penalty laws.