Is it true that a parent can be forced to testify against a child in a criminal trial?

Yes. There is no parent-child privilege. Remember Marcia Lewis, the mother of Monica Lewinsky, who left the courthouse physically ill after being forced to testify before the grand jury about her daughter and President Clinton? The general rule is that all relevant evidence is admissible in criminal trials. Testimonial privileges protecting communications between two individuals are exceptions to this rule and must be specifically recognized in the law. Examples of such privileges are communications between spouses, doctor or psychotherapist and patient, attorney and client, and priest and penitent. Many scholars and others argue that the sanctity of the family relationship and the right to privacy justify the creation of a family privilege. By protecting communications made in confidence between parent and child, they argue, a privilege both preserves the right of privacy of the relationship and even more importantly, encourages open communications between the parent and child. Exceptions are made to all privileges for what is called the "crime-fraud" exception where both parties are participants in the crime charged. If a family privilege is ever enacted, an exception will likely be built in so that it would not apply to cases where one parent committed a crime against the other or their child. Only one federal court to date, in Nevada, has recognized a parent-child privilege. Until such a privilege is created by Congress or state legislatures, a parent can be made to testify against their child in a criminal trial.