If the prosecutor decides to seek the death penalty, then certain trial procedures come into play. The district attorney has to give the defendant at least 30 days notice before trial if the death penalty is sought. All 12 jurors must agree that the district attorney has proven some aggravating factors and those factors outweigh any mitigating factors presented by the defense. Furthermore, the State must prove those aggravating factors beyond a reasonable doubt before the jury could sentence the defendant to death. If not, the jury can sentence the defendant to life without parole or life if no aggravators are found.
All murder cases are horrible.
Each is heinous and inexcusable. But each is not a death penalty case. All the legal criteria must be met before the district attorney can seek the death penalty. That decision is solely the chief prosecutor's and it is a tough one. It cannot be based on a popularity poll and it can't be delegated to an assistant.