As a criminal defense lawyer, it is understood that prosecution witnesses always come with their own baggage. We have all represented them. If they are going to drag their feet on the way to the witness stand, there are ways to turn their reluctance into a refusal to testify.
The prosecution may offer immunity to a reluctant witness, which forces their testimony subject to a contempt sanction, right? Not so fast. If you are in state court and there is federal criminal exposure (drugs, firearms, etc.), courts will find that the witness is entitled to insist on federal immunity as well. Interestingly, that is even more complicated than it sounds. In a recent triple murder defense here in Maine, the U.S. Attorney’s Office would not grant immunity for witnesses with potential drug exposure. The only thing the feds would confirm in writing was that they did not have a present interest in prosecution. Although most witnesses caved and took the stand, at least one did not, which was no small thing at the time.
The opposite federal-state tactic does not work because a federal prosecutor’s grant of immunity is binding on state prosecutors, so a witness’s claim of state criminal exposure in a federal criminal trial will be of no avail.
The prosecution witness may not have been exceptionally honest and forthcoming with the police, which the witness to false public report prosecution. If the prosecution decides to grant immunity, then the government tainted with granting a license to lie.
Courts should appoint counsel to prosecution witnesses with potential incrimination issues. Your speaking with those witness lawyers about the legal risks of testifying can be very important, especially when witness counsel is unfamiliar with federal criminal law and the federal sentencing guidelines. In my cases, witness counsel have told me their clients were willing to take a chance on testifying, but the lawyers went back to their clients after I informed them their clients faced potential mandatory minimum sentences, would be subject to cross-examination under oath regarding their criminal activity, and would serve any resulting federal sentence out of state and away from family. If the court declines to appoint counsel for a reluctant witness, the Court may grant you limited voir dire to develop the issue.
In the end, most reluctant witnesses become unreluctant because the prosecution holds most of the important cards. Sometimes the witness’s reluctance is just a show or they are trying to bargain for complete immunity for all past crimes. The latter obviously never materializes, but the witness may become so dissatisfied with the process that they decline to testify on Fifth Amendment grounds or they may be more defense friendly during their time on the stand.