The first thing I always recommend to people preparing for a child's deposition is to read several of the many good publications about forensic interviewing of children. Not everything in those guidelines will be relevant to your case, and most of them are geared toward sexual abuse investigations, but the guidelines synthesize many years of study and experience about how best to ask children questions about specific events. Some of the publications I recommend are the NIHD Interview Protocol (also explained in the Journal of Law and Contemporary Problems), theAPSAC Practice Guidelines on Investigative Interviewing, and the Michigan Forensic Interviewing Protocol.
The next thing I recommend is . . .
Find a neutral, child-friendly location
A local child advocacy center may be able to accommodate you, and usually has the best facilities for questioning children. A therapist's office is a good option, or even a school counselor's office. At all costs, avoid a law office conference room where you're sitting across an adult-sized table.
In fact, avoid using a table at all. Sit in comfortable chairs at a conversational distance, where you can just chat with the child. With very young children, you may need to join them on the floor and engage in their play with toys. In fact, as noted below, use the toys to help them tell the story.
Hide the court-reporter and videographer
Make the court reporter and videographer as unobtrusive as possible. Set them up in a corner, introduce them to the child, explain why they are there, and then ignore them. You will need a very good court reporter, but, unlike most depositions, this one needs to be all about the child, not the transcript.
You may not need an oath
With a very young child, try to get an agreement from opposing counsel about whether or not the court reporter actually has to administer an oath. Most jurisdictions don't require a formal oath for testimony from very young children. Florida, for example, provides that "a child may testify without taking the oath if the court determines the child understands the duty to tell the truth or the duty not to lie." Fla. Stat. Sec. 90.605(2) (2006). See also, State v. Hanson, 149 Wis. 2d 474, 482, 439 N.W.2d 133, 137 (1989) (court may dispense with oath with young child).
If your jurisdiction is one of those, you can simply establish that the child understands his or her obligation to tell the truth. See, e.g., Smallwood v. State, 165 Ga. App. 473, 301 S.E.2d 670 (1983) (four-year-old child's statement that "Jesus don't like it [if] you don't tell the truth" sufficient to establish competency); State v. Avila, 78 Wn. App. 731, 899 P.2d 11 (1995) (five-year-old's description of clothes and objects, and agreement that it was important to tell the truth were sufficient). If you are not certain what questions to ask, call the prosecutor's office in the jurisdiction governing the deposition, and talk to the prosecutor who handles the child victim cases.
Note, however, that all of the law I've found deals with testimony in court and speaks in terms of the judge's discretion. In a deposition, without a judge to make a ruling then & there, you need to have agreement of opposing counsel about how you proceed to establish the child's competency as a witness.
Get Acquainted
At the beginning of the deposition, spend some time just chatting with the child. Ask about things that interest him or her, and try to set them at ease before getting into specific questions. The protocols I listed above have some very good pattern questions.
Keep It Simple
Be sure to ask simple questions using simple words. When children don't understand a question, they have a tendency to just agree with the adult. If your question is too complicated or above the child's comprehension, you are not likely to get an accurate (or even understandable) answer.
Understand Their Vocabulary
If the child is very young, do some research on cognitive and communication skills at various ages. Preschool children think concretely, and therefore use nouns instead of adjectives or adverbs. For example, a child who talks about a knife may mean "painful." A child who does not have the vocabulary to describe pain, will reach for a concrete object within his or her knowledge.
Let Them Play
If the child is preteen or younger, bring an art pad and crayons or markers with you. Children lack an adult's vocabulary, and sometimes run out of words. They are more at home with concrete objects, and sometimes can explain themselves better through drawings. Get them to draw the scene, and then describe it to you. It is simple enough to make the drawing an exhibit to the transcript, and you are much more likely to get good information.
For very young children, bring toys with you to represent the events you are asking about. Toy cars and trucks, for example, would help a child tell about a car accident. Be sure to have enough miniature people (I like the Little People series) to represent the people involved in the events.
Take Your Time
Finally, be patient. You may have to ask the same question different times or in different ways. Do not expect a child to enter your world. You will have to enter their world, and try to remember what it was like.
The Minnesota Court of Appeals recently issued an interesting opinion, looking at what formalities are required to accept children as witnesses. In the Matter of Welfare of J.J.W., No. A09-639 (Minn. App. Feb. 9, 2010) involved a four-year-old child's testimony about sexual abuse by a 16-year-old relative. 