Thank you again for your question. I should start by saying that because the nuances of every case are different, this information should not be construed as complete or advice without consulting in person with counsel. That said, the answer to the question of whether it is legal for the prosecution in a criminal case to offer a plea deal that includes restitution where the actual restitution owed is unknown is "yes", as long as the prosecution has probable cause to believe that the actual restitution equals or exceeds the amount offered in the plea deal.
Although the prosecutor's burden of proof
in court is guilt beyond a reasonable doubt, the prosecutor's ethical obligation is to not prosecute any crime unless there is at least probable cause to believe that the crime has been committed. Where restitution would be due, the prosecutor's obligation would be to only seek that restitution for which there is probable cause to believe is owed to the victims.
Any type of litigation
, including a criminal prosecution, is a fluid situation--evidence comes to light during the course of the process that will oftentimes alter or reduce the charges and related restitution. It is possible, and even likely, for any given case that the prosecution may know that a certain amount is owed by a defendant at the onset of a case, but not have a firm determination of the amount until later in the prosecution.
To give an example, you may have a violent criminal who injured their victim causing $10,000 in medical expenses. Initially, it is clearly known that the victim's medical bills equal $10,000, but there may be complications that manifest much later that would raise the victim's medical expenses. The prosecution may nonetheless offer a plea deal that includes restitution of $10,000. As long as the prosecution is not seeking restitution in excess of what it has probable cause to believe is owed, it has the power to settle.
I again thank you for your patience, and I am sorry that you experienced technical problems at the onset of this exchange. I do hope to provide you with satisfactory service. Please feel free to let me know if clarification is needed. One you are completely finished, please feel free to positively rate me--it does not cost anything extra to do so, and it is how I am compensated. Thanks.