Q: Does a victim of a heinous crime have the ability to appeal a plea bargained sentence?

A: The defendant has to be on parole. You will need to call the district attorney regarding your sister but I doubt there is anything that they can do,

A: I am sorry for your family's loss, but I do not believe the courts are capable of providing the closure you seek. The limitation period for criminal attempt is the same as that of the offense attempted. 12.03(a) TxCCP There is no limitations period for murder. 12.01(1)(A) TxCCP. That said, it is highly doubtful that a case like this would be filed and, if it were, it would probably not survive a constitutional challenge pursuant to the 6th and 14th Amendments. (Speedy Trial and Due Process of Law). The government has known about this crime for 15+ years AND also known the exact whereabouts of the suspect because he was in state custody.

I believe that even if a magistrate judge could somehow be convinced that the crime against your sister was not contemplated in the original plea deal, any new attempted murder case against the killer at this point would go nowhere and be a waste of prosecutorial and judicial resources.

Contrary to the depictions that appear in popular media, the victim of a crime doesn't actually have the right or ability to file or press charges. They can report an offense to law enforcement, but the cops have the duty to decide whether to initiate an investigation and the prosecution has the duty to decide whether or not to actually move forward with a case. (There are some situations where the prosecution initiates a case without law enforcement, but those are rare.)

Another fallacy depicted in popular culture is that appeals are essentially a "do-over" but that's not true either. Appeals are generally limited to mistakes made by the trial-level court over one party's objection. If nobody objects then the issue is not "preserved for appeal." In short, appeals are not available to litigants who are simply dissatisfied with the result. The courts of appeals typically allow all but the most egregious mistakes to slide because the concept of "you really had to be there to understand" applies in the courtroom as much as anywhere. Generally speaking, a new trial is only appropriate when a legal mistake was both so obvious that it never should have been made, AND the correct decision was so pivotal that it would have substantially changed the result. Even a new trial is not a true do-over because the litigants may be limited by their previous testimony. Such things DO occasionally happen, but they are much less common than most people believe.