Criminal Law Questions? Ask a Criminal Lawyer.
First of all, a prosecutor IS a lawyer. I am in court every single day on criminal law issues, so suffice it to say I have a great deal of experience in the issue of illegal searches and seizures, and in the area of narcotics prosecution.
The reason I am asking about your county is because every county has different standards for their probation searches. If you don't want to tell me the county I can give you an either/or answer.
First, yes, the state can file charges against you months later, or at any time within the statute of limitations period. Four months is well within the time period allowed by law. Second, you can be prosecuted for possession. The statute merely requires that you possessed any quantity of a narcotic. Any quantity includes residue. The reason there was a delay in the charges was that the prosecutor likely wanted to wait for the lab results to see if there actually was a testable residue on the paraphernalia. As for whether the search was illegal, it depends on whether it was in compliance with the probation standards for your county. If it was not, a lawyer can easily make a suppression motion and have the evidence tossed out at trial.