Detecting Children’s Lies in Depositions and Interviews

A scholarly article on deception by children prompts ideas for questioning adverse child witnesses in pre-trial interviews and depositions.

The article, “Children’s lies and their detection: Implications for child witness testimony,” by psychology professors Victoria Talwar and Angela M. Crossman, appears at 32 Developmental Review 337–359 (2012). It is a review of research findings on deception by children.

Lying is merely one way for children to make false allegations. Children also may give false reports, even of events they say they have personally experienced, because of memory errors. This review looks only at lying.

The review discusses studies confirming that very young children rarely can maintain a lie. During the elementary school years, though, most children develop the mental capacity to lie well.

In many states, attorneys for those accused of child abuse are permitted to interview or take depositions of child complainants before trial. Some of the research findings in the article suggest questions for such interviews.

Ask for a commitment to tell the truth

Investigative interviews of children by police and child protection workers usually include questions about telling the truth and lying. These questions are asked primarily to determine the child’s competency as a witness. (I have written several times on developments in the law concerning a child’s competency as a witness, most recently here) This portion of the investigative interview commonly ends with an instruction or request to tell the truth in the interview.

Some research, at least, shows that when children commit to tell the truth, they are more likely to do so. This raises the possibility that a child who had made a false allegation—to a parent, perhaps—would not repeat it after committing to tell the truth. Hence the attorney for the accused may want to ask the child to make that commitment in a pretrial interview or deposition.

Suppose the child commits to tell the truth in the pretrial interview and then repeats her allegations about the defendant. Will this damage the defense?

Not likely. The child probably promised to tell the truth in the law enforcement interview in which she made the allegations. The child will make the same promise when testifying. Thus the promise in the defense attorney’s interview won’t add to the credibility of the allegations.

Increase “cognitive load”

The review notes that lying is hard mental work. The liar must carry a heavy “cognitive load,” as psychological researchers put it.

Alongside his memory of what truly happened, a lying witness must keep in mind the alternative version he is reporting. He must also remember that, if his lie were true, he wouldn’t know certain things he actually does know; hence he cannot say anything that shows he does know them. This is why very young children cannot maintain a lie for long.

But even an adult’s maintenance of a lie can collapse as the cognitive load increases. Some police interrogators have uncovered adults’ lies through simple devices to increase cognitive load, for example, directing the subject to tell what happened in reverse chronological sequence.

The simplest way to increase a witness’s cognitive load is to ask follow-up questions. Child interviewing protocols in widespread use by law enforcement help interviewers do this. (An excellent example is Washington State’s Child Interview Guide.) These protocols can help attorneys for the accused ask good follow-up questions, too.

Because children’s cognitive capacities generally don’t match those of adults, some of the techniques for increasing an adult’s cognitive load shouldn’t be used in a defense interview of a child. Asking a seven-year-old to tell what happened in reverse order might confound a child who is telling the truth. (And for the child who truly has been abused, it might seem a callous attempt to make a game of a distressing experience.)

Another suggestion in the article is more useful with children: ask unanticipated questions. By the time the attorney for the accused gets to interview the child, the child has probably been interviewed several times by others. She has probably come to expect interviewers to want her to report certain things about the event. By coming up with questions about other aspects of the event, an imaginative attorney may derail a lie.


The authors of the review acknowledge that research on many aspects of children’s lying is scant. For example, in most experiments, the interviews in which children have been tempted to lie have been much shorter than many forensic interviews, and without the repeated interviewing common in legal proceedings.

Also, the stakes can be enormous in legal settings; a child’s testimony can send a parent to prison—or permit someone who is abusing children to continue doing so. It would not be ethical, though, to conduct experiments in which children were led to believe their reports could have such grave consequences. So far researchers have not found a way to overcome this mismatch between experimental and forensic conditions.