The first thing a parent in this situation should understand is what not to do. Do not engage in extensive or prolonged questioning of a child. The best thing to do is to contact the local department of social services or an experienced child therapist [I emphasize experience is vital here since the warning signs and symptoms of child abuse are many and difficult to interpret].
It is vital that the child’s outcry or description of abuse be made to a responsible professional. It would be a little bit of an overstatement that a child’s statement to their parent is never believed by the legal system. But there is significant skepticism about statements a child makes to a parent but not to other responsible professionals. There is legitimate research that indicates that the way children describe incidents may be significantly influenced by what they think adults expect to hear.
When discussing any concern of sexual abuse with children, it is extremely important to ask very open-ended questions. Unfortunately, it is often difficult for a parent to obtain enough information to know whether a concern is founded. More unfortunately, after many conversations between a parent and child, the suspected influence of the questioning parent may make it more difficult to protect a child.
The very painful reality for concerned parents is that it is possible to increase the risk of danger to a child by prolonged questioning. While children may feel most comfortable in confiding to the most trusted adult in their life (a parent), it is a tragic irony that too much conversation between a parent and a child actually may result in being harm to that child. Sometimes restraint is the best assistance a parent can give to their child.
*The information given in this answer represents the authors own observations over many years. The extent to which “the system” does or does not appropriately respond to these concerns is hotly disputed. The author has seen situations both where “ the system” has been under protective of children so that abuse is continued for extended periods of time and also where innocent parents have been unfairly blocked from access to their children or suffered other serious consequences wrongfully.
The author respects that there are many valid perspectives that “the court system” is either under or over protective of children. Rather than engage in a philosophical debate on this topic, he intends to provide practical, common sense advice, which is usually a prerequisite for obtaining concrete protection for children.