I ran across an outstanding article that describes a common dilemma for lawyers working with child witnesses, which is figuring out much we can rely on the child's memory.  The problem goes beyond our usual formulation of whether or not a witness is lying.  The dilemma is that children can form actual, real memories of things that they never witnessed.  In this article, the memories were benign and positive (activities with a deceased grandfather), but the dynamic can be the same when memories matter in criminal or civil cases.

Researchers have labelled the problem "source monitoring," i.e., children cannot keep straight the sources of their information.  An event they have only heard about can be just as real to them as an event that they experienced.  Studies have shown, for example, that younger children can become confused about information from different, but similar, sources.  Other research indicates that preschool children are more susceptible than older children, and that children become less suggestible as they mature.   As the article noted:

 "Through early adolescence, children's ability to remember exact details is poor relative to adults, which makes them especially prone to false memories arising from suggestion," says Charles Brainerd, Ph.D., a professor of psychology at Cornell University. Dr. Brainerd adds that children’s memories become reliable much later than you might guess, at around 9 or 10 years old. And because our brains are still developing through our mid-20s, suggestibility doesn’t reach its low point until young adulthood.

Another interesting finding is that older adults have more source monitoring difficulties than younger adults, indicating that the process may be related to brain development rather than emotional maturity.

This source monitoring problem means that attorneys, law enforcement, and forensic examiners have to be careful in how they question children.  We know, for example, that how an adult phrases a question can change a child's answer, and that  repeated questions may elicit different responses.  Cross-examination-style questions, according to one study, "appear to be particularly detrimental to obtaining accurate event reports from children."  Lawyers' cherished beliefs in the value of a rigorous cross-examination for obtaining the truth, then, are simply wrong when it comes to children.

If we truly want the truth, as opposed to our preferred narrative, then we need to be aware of all of these facts when we question children about their memories of an event.  We also need to know who else has questioned them, and how, in the intervening time.  It may be that well-intended but flawed questions, and the normal passage of time, have so impacted a child's memory that we will never what they witnessed and what they learned later from another source.