Final answer:
The prosecutor can prosecute a witness if they can establish a prima facie case, regardless of immunity.
Step-by-step explanation:
Under the Sixth Amendment, the prosecution has the right to present witnesses in a criminal trial. However, regardless of a witness's immunity, if the prosecutor can establish a prima facie case against that witness, they can prosecute them. A prima facie case is one where the evidence presented is sufficient to establish a fact or justify a legal conclusion, unless it is rebutted or contradicted by other evidence. Therefore, a witness can still be prosecuted if the prosecutor can demonstrate that they have enough evidence to establish a prima facie case against the witness.