Is there any statutory authority that bars a crime victim from making a request for restitution from the defendant?

I am getting a public defender that is asking a judge to deny restitution claims because the request for restitution is not timely; couple of months from date of sentencing.

There is no such law that required a victim to do anything in connection with a request for restitution tied to a criminal sentence. As one might expect, the prosecutor is the one with the authority to ask for restitution, prove up the amount and tie it to the offense. I also know of no notice or timing requirement.

Our "offer sheets" specify that if the amount of restitution is left blank, that it is subject to a hearing at a later time. If we forget (it happens sometimes - gasp!) to include restitution on our paperwork, we will usually ask the probation officer to have the defendant voluntarily agree to the restitution. Many times they won't, which is dumb because they know they owe it, they're just trying to avoid paying it, but then they have to come back to court, have a hearing, pay their lawyer, etc. and it's a lot more trouble for them.

p.s. If I know that realistically the defendant will never be able to pay the amount of restitution owed during their term of probation (or they're simply taking jail time), rather than setting them up to extend them (or fail outright) I will usually talk to the victim about getting legal advice to go after the defendant civilly - they have more resources that way anyway since they can attach property to their civil judgments (whereas if the D fails to pay during probation, or doesn't complete probation in other ways, well, D can go to jail, but that doesn't help the V much - not that attaching D's assets will help much either, but it's another option).