Questions to Ask an Expert Witness
For a new attorney, a law student or a self-represented party who has to hire, depose or examine an expert witness, whether that is a doctor, an engineer, a forensic analyst or an accountant. The list follows a case in order, each question with a note on what a good or a worrying answer sounds like: what to ask before you retain an expert, the deposition of the other side's, qualifying an expert in court, direct examination of your own and cross-examination of theirs. The names and figures in the cross questions are samples to swap for your own, the rules on experts differ from court to court, and none of this is legal advice.
The questions
Each question, and why to ask it
Before Hiring
Is the question in this case squarely inside what you do for a living, or should I be talking to a different kind of specialist?
Why ask it
Describe the dispute first, down to the procedure, the material or the type of account. A good sign is an expert who draws the line unprompted ('the surgery is mine, the infection afterward is not') and tells you who handles the other part. One who claims the whole case will be asked on cross how often they have done each piece of it.
Have you ever worked for, with or against any party, law firm or insurer involved in this case?
Why ask it
Ask this before you share anything confidential, and name every party and firm out loud. A past job for the other side does not always rule an expert out, but how conflicts are treated depends on the court, so check your rules before you send the file.
How much of your working week is spent doing this work, and how much reviewing cases for lawyers?
Why ask it
The answer you want is someone who still operates, builds, audits or tests most days and takes a few cases a year. If most of the income is from lawsuits, expect the other side to open its cross there, and ask how the expert has answered that before.
How many times have you testified at deposition and at trial, and for which side each time?
Why ask it
Ask for the list in writing, since many courts make a testifying expert disclose one anyway. A roughly even split is the easiest to defend. A lopsided one is workable if the expert can explain it in a sentence without sounding stung.
Has a court ever excluded or limited your testimony, or criticized it in a written ruling?
Why ask it
Opposing counsel will search for this, so you need to hear it first. One exclusion with a clear explanation can often be lived with. The worrying answer is a flat 'never' that a short search of published rulings contradicts, so run the search yourself.
Is every line of your resume accurate today, and has a licensing board or professional body ever disciplined you?
Why ask it
Small inflations do the damage: a certification that lapsed, 'author' on a paper with nine names, a hospital post that ended years ago. Many licensing bodies keep a public record, so look it up whatever the answer is, and ask for a corrected resume before one goes to the other side.
What have you written, posted or said under oath that could be quoted against the opinion I am asking about?
Why ask it
Think of articles, conference slides, old transcripts and social media. An expert who once took the other view in print is not out of the running, but needs a short, honest account of what is different in this case.
What do you charge for reviewing the file, writing a report, a deposition and a day at trial?
Why ask it
Get the fee schedule in writing, because rates often differ by task and the surprises are in travel time, cancellation fees and minimum days. Then ask for an estimate for the first review alone, and approve further work in stages.
From what I have told you so far, what would you need to see before you could say whether you can help?
Why ask it
A careful expert answers with a list of records. One who gives you a conclusion over the phone has shown you how they will sound on cross. Tell them the bad facts along with the good ones, or the list will be the wrong list.
If the records do not support my position, will you tell me so before you write a report?
Why ask it
You are paying for an honest reading, and an early 'I cannot support this' can save the cost of a case. Whether an expert's notes, drafts and messages can be demanded by the other side depends on the court, so learn that rule at the very start.
Now that you have read the file, what are the weakest points in the position you would be supporting?
Why ask it
An expert who cannot name one has either not read closely or is telling you what you hope to hear. Write the answer down: it is a preview of the other side's cross and a list of what you will need other evidence for.
Can you explain the central idea in this case to me the way you would to someone with no background?
Why ask it
Have them do it on the spot, in about two minutes. You are listening for short sentences and one everyday comparison, because a long list of credentials is no help when the judge or jury cannot follow the explanation.
Will you do all of the work yourself, or will assistants and colleagues handle parts of it?
Why ask it
Staff often take the measurements, run the numbers or summarize the records, and that is ordinary. The testifying expert still has to be able to stand behind every piece, and the other side may ask to question whoever did it, so get the names.
Can you meet the court's deadlines for a report, a deposition and trial, and how much notice do you need?
Why ask it
Read the dates out. Working surgeons, engineers and accountants are booked months ahead, and an expert whose report arrives after the deadline may not be heard at all. If the trial date moves, ask what a rescheduled day costs.
Deposition
Does your report contain every opinion you intend to give in this case?
Why ask it
You are hoping for a plain yes. If the expert hedges, ask what else there is and take each addition in turn before you move on. How strictly a court holds an expert to the report depends on its rules, but the transcript will show what you were told.
How was your assignment described to you, and did it change at any point?
Why ask it
The scope explains the gaps: an engineer asked only whether the roof leaked was never asked why. Follow up with whether there was any question the expert was told to leave alone, and who said so.
On what date were you first contacted, and by what date had you reached the opinion in this report?
Why ask it
Set the two dates against the invoices and against the dates the key records were sent. An opinion formed after two billed hours, or before the photographs arrived, is something to bring out calmly at trial, not to argue about now.
Is this your entire file, and is there anything you created or received that is not in it?
Why ask it
Go through it item by item on the record: notes, calculations, photographs, test data, invoices, emails. When something is described but not produced, ask where it is kept and who could get it. Drafts and exchanges with the hiring lawyer are protected in some courts and open in others, so know which you are in before you press.
What did the lawyers who hired you send you, and what did you ask for that you never received?
Why ask it
This shows whether the expert saw the whole record or a chosen slice of it. 'I asked for the maintenance logs and did not get them' is one of the most useful sentences you can leave with, so ask why they wanted them.
Did you speak with either party, any witness or anyone else involved, and did you keep notes of what they said?
Why ask it
What an expert was told on a phone call can carry as much of the opinion as the documents do. Get the date, who else was on the line and what was said, then ask for the notes. If the expert spoke to nobody, ask why paper alone was enough.
What assumptions did you make where the records were silent or in conflict?
Why ask it
Experts fill gaps, often by taking the hiring side's witness at their word. Get every assumption listed with where it came from. Any that rests on a disputed account is a cross question waiting for trial.
Has the method you used been tested, and what is known about how often it gives a wrong result?
Why ask it
Meant for laboratory and forensic opinions, such as a drug test, a handwriting comparison or a tool-mark match, though it works on any formula or software. Ask where the figure is written down and whether a second person checked this particular result. 'It is never wrong' is an answer to press on.
Which textbooks, standards, codes or journals do you treat as reliable in your field?
Why ask it
Write down titles and editions. If one of them disagrees with the opinion, you have the start of a cross question for trial. An expert who accepts no authority at all has also told you something.
What work have you not finished, and what do you plan to do between now and trial?
Why ask it
Listen for more testing, another site visit or a supplemental report. Ask to be told when any of it happens, and read your court's rule on how late a new opinion may be served.
Which parts of my expert's report do you agree with?
Why ask it
The agreements are what you came for. Take the other report section by section and collect each 'I do not dispute that', because every one narrows the trial and gives your own expert firmer ground.
What fact, record or test result would lead you to change your opinion?
Why ask it
A deposition is the place for an open question like this, since a bad answer costs you nothing in front of a jury. A careful expert names something specific. Your next job is to find out whether it exists.
Qualifying
Where do you work now, and what does an ordinary week in that job involve?
Why ask it
The first thing a judge or jury learns should be what this person does when no lawsuit is involved. Two or three sentences on the patients, sites or accounts they handle is enough, and the degrees that follow then have something to hang on.
What degrees, licenses and certifications do you hold, and is each one current?
Why ask it
Work from the resume and move through it briskly, with a phrase from the expert on what each credential took to earn. If the other side offers to accept the qualifications, ask how your judge handles that, since many advocates still want the highlights heard.
About how many times have you personally handled the kind of problem at the center of this case?
Why ask it
Standing in a field is not the same as hands-on experience with this procedure, this structure or this kind of business, and the narrow match is what the other side will test. When the number is small, bring it out yourself and have the expert say why their training still covers it.
Have you taught, published or presented on the subject you are here to talk about?
Why ask it
Choose the two or three items that bear on the point in dispute and skip the rest of the list. 'She wrote the chapter trainees learn this from' stays with a listener. Forty article titles do not.
Have you been accepted as an expert witness in this field before, and in what kinds of courts?
Why ask it
A count and a type of court is enough. A first-time witness should say so without apology and go straight back to their hands-on experience. How a witness is formally offered as an expert, and whether that step exists at all, depends on the court.
What field, exactly, are you offering opinions in today?
Why ask it
The answer sets the fence. With your own expert, phrase the field no wider than the opinions need: 'residential roofing' is easier to defend than 'construction'. With the other side's, a wide answer gives you room to show where the experience stops.
What are you charging for your time on this case, and does any of it depend on who wins?
Why ask it
Ask it yourself, early and without fuss, so the fee is not a reveal on cross. The answer should be a rate, the hours so far and a plain no to the second half. If the honest answer to the second half is anything else, you needed to know at hiring: fees tied to the result are barred or frowned on in many places.
Your training and your daily practice are in a different specialty from the one at issue here, correct?
Why ask it
This one is for the other side's expert, if your court lets you question qualifications before the opinions begin. Keep to the gap between what the witness is trained in and what they are about to say. Where the gap is small, skip it: a failed challenge ends with the judge accepting the expert while everyone watches.
Direct
What question were you asked to answer in this case?
Why ask it
One sentence, in words the listener will hear again in your closing. It tells the judge or jury what to listen for and keeps the expert from sounding as if they were hired to reach a result.
Which records did you rely on most, and did you ask for anything beyond what you were first sent?
Why ask it
Have the expert name the main items and say in a phrase why each mattered. The second half is the useful part with your own witness: 'I asked for the full chart and received it' answers the hand-picked-file attack before it is made.
Did you examine the person, visit the site or handle the evidence yourself?
Why ask it
Firsthand work carries weight, so let the expert describe the day and how long it took. If the opinion rests on records alone, have them say why records were enough for this question. Leaving it unsaid hands the other side its first cross question.
What method did you use, and is it the one you would use in your ordinary work outside a lawsuit?
Why ask it
Judges deciding whether to hear an expert tend to care about the method more than the conclusion. A strong answer names it, says where it is taught or published, and confirms nothing was invented for the case. The test a court applies differs by place, so read yours before you draft this part.
Take us through what you did, one step at a time.
Why ask it
Break the answer up yourself: 'What did you do first?' 'What did that show?' Stop at every technical term and ask what it means. Three minutes of unbroken lecture is where a listener is lost.
Would a diagram, a model or a photograph help you explain that?
Why ask it
The usual way to get an expert out of the chair and teaching. Ask ahead of the hearing whether visual aids must be shown to the other side or approved by the judge first, and rehearse with the real thing, not a description of it.
Based on that work, did you reach an opinion about what caused the retaining wall to fail, and what is it?
Why ask it
Everything else on direct is built around this answer, so have the expert give it in one plain sentence and stop. Some advocates ask it straight after the assignment question, so the listener knows where the method is heading. The retaining wall stands in for your own issue.
Do you hold that opinion to a reasonable degree of certainty in your field?
Why ask it
Many courts expect an expert's opinion to meet a set standard, and some expect a particular phrase. The wording differs by place and by field, so find out what yours wants and have the expert say exactly that. An expert who answers 'it is possible' may not have given an opinion the court can use.
What are the three strongest reasons for your opinion?
Why ask it
Asking for three forces a ranking and gives the listener something to count. Have the expert tie each reason to an exhibit already in evidence, by number, so that it can be found again later.
I am going to ask you to assume certain facts are true. On those facts, what is your opinion?
Why ask it
A hypothetical is one way an expert who was not there can give an opinion on your version of events, and some courts expect it more than others. Write it out and read it, because each assumed fact needs evidence behind it and a fact left out is what the other side will add back on cross.
What other explanations did you consider, and what ruled each one out?
Why ask it
Name the other side's theory in the question if the expert does not. The answer that persuades points to one fact that cannot be squared with the alternative, such as a date, a measurement or a lab value.
The other side's expert reached a different conclusion. Where exactly do the two of you part ways?
Why ask it
Ask your expert beforehand to keep this answer respectful, since sneering at a colleague costs more than it gains. The useful answer shrinks the dispute to one assumption or one measurement and says why this expert's version is better supported.
Is there anything in the records that does not fit your opinion, and how do you account for it?
Why ask it
Every file has one awkward page. Heard first from your own expert, in their words, it sounds like candor. Heard first on cross, it sounds like something that was being kept back.
What are the limits of your opinion: what can you not tell us?
Why ask it
Most useful where the answer is a range, such as a valuation, a speed or a time of injury. Have the expert give the range, say why they landed where they did inside it, and state plainly what the evidence cannot show. Listeners tend to trust the rest more for it.
Cross
You agree with Dr. Alvarez that the crack was already visible in the first inspection photographs, correct?
Why ask it
Open with the points of agreement you collected at the deposition, while the witness is still inclined to be agreeable. Dr. Alvarez and the crack are stand-ins for your own expert and your own fact. Each yes lends the other side's credibility to your case.
This is not the first case you have taken from the defendant's law firm, is it?
Why ask it
Know the number before you ask, from the expert's disclosed case list or the deposition, and make it your next question: 'The sixth, correct?' Repeat business makes the point by itself, so go on to the next topic without remarking on it.
You have billed sixty-two hours on this case up to today, correct?
Why ask it
Have the invoices in hand so the figure cannot drift, and put your own total in place of the sixty-two. Resist adding that the opinion was bought: most experienced experts have a calm reply about being paid for time, and the number does its work without your help.
Nine of the ten cases on your disclosed list were for the side that hired you today, correct?
Why ask it
Count them yourself beforehand and ask only if the tilt is steep. If the split turns out closer to even than you assumed, cross this question off, because the answer would help the witness. Some courts also limit how far you may go into an expert's other work and income, so ask what is allowed.
You have never examined the plaintiff yourself, have you?
Why ask it
Use it when it is true of their expert and not of yours, and it works the same way for a site never visited or a machine never handled. The natural follow-up is how many hours the invoices show for reviewing records. If your own expert also worked from paper, leave it out.
You did not see the maintenance logs before you signed your report, did you?
Why ask it
Pick two or three missing documents that matter and that the judge or jury has already been shown. Then stop. Asking whether the logs would have changed the opinion invites 'no, and here is why' unless the deposition gave you a yes.
Your opinion takes the plaintiff's own account of the fall as accurate, correct?
Why ask it
This ties the opinion to a witness whose reliability you are contesting elsewhere. The follow-up is short: 'You did not check that account against anything else.' Save the conclusion for your closing.
Assume instead that the floor had been dry for an hour. On that assumption, your conclusion about the cause would be different, wouldn't it?
Why ask it
Here you feed your version of the facts into their method. Each fact you assume needs support in the evidence. A careful expert concedes the point, and one who will not move on any set of facts starts to sound like an advocate.
You told us at your deposition that this textbook is a standard reference. Did I read this passage from it correctly?
Why ask it
Read the passage word for word and ask nothing more than whether you read it right. The steps for putting a published work to an expert vary by court, so learn them first, and bring the page marked.
In an earlier case you testified that this same method could not be relied on, didn't you?
Why ask it
Old transcripts and articles are where experts contradict themselves. Have the page and line open in front of you before you ask. If you cannot put the earlier words in the witness's hands, do not ask the question.
As an engineer, you are offering no opinion on the injuries themselves, correct?
Why ask it
Experts drift past the edge of their field when the questions get friendly. A clean 'no opinion' in the transcript is something to point to if it happens later, and tells the listener which parts of the testimony to set aside.
You cannot rule out that the pipe was already leaking before the renovation, can you?
Why ask it
Most experts have to concede that something is possible, and the redirect will be 'possible, but unlikely'. Ask it only when you have a fact that makes the other cause more than a possibility, and put that fact in the next question.
You did not check the company's sales figures against its bank statements or tax returns, did you?
Why ask it
Aimed at valuation, lost-profit and other number-driven opinions, where the result is only as sound as the inputs. Find out at the deposition which numbers were handed over and which were verified, and ask about the unverified ones only.
No written standard or code section requires the step you say was skipped, does it?
Why ask it
For standard-of-care and building cases, and safe only when the deposition showed there is nothing to point to. If the expert can open a codebook to the page, you have helped them make their point, so know the answer before you stand up.
Working with an expert witness, from the first call to cross
Practical guidance for the conversation itself
Choosing and preparing your own expert
Look for someone who still does the work
Start with people who treat patients, inspect buildings or keep books for a living, and ask colleagues or a professional body who they would trust on the question. Directories of professional witnesses exist and can help, but an expert found through one may be asked about it on cross.
Send the whole file, bad pages included
An opinion built on half the record falls apart when the other half is put to the expert on cross. Send everything relevant, keep a dated list of what went and when, and say which facts are disputed so that nothing is assumed by accident.
Learn what the other side can see
Courts differ on whether an expert's drafts, notes and messages with the hiring lawyer must be handed over. Find the rule for your court before the first email, and write to the expert on the footing that it could be read aloud.
Check the deadlines for disclosure
Many courts set a date for naming experts and, often, for serving a written report, and a late expert may not be heard. Read the scheduling order, or ask the clerk or the court's self-help center, and give the expert the dates on the first call.
Rehearse the cross, not only the direct
Play opposing counsel for half an hour: the fees, the missing documents, the weakest fact. The aim is for the expert to have heard each hard question once already. It is not to script the answers, which have to remain the expert's own.
Qualifying an expert in court
The usual order
Credentials first, then hands-on experience with this kind of problem, then teaching or writing, then any earlier testimony. In some courts you finish by formally offering the witness as an expert in a named field and the judge rules. In others you go straight on to the opinions unless there is an objection. Ask which yours does.
Name the field narrowly
Offer the witness in the smallest field that covers the opinions you need. A wide label invites questions about everything inside it that the expert has never done.
When the other side offers to accept the qualifications
The offer saves time, and it can also keep an impressive resume from being heard. Many advocates accept and still ask a few short questions on the highlights. Whether the judge allows that is a matter of local practice, so ask before the hearing.
Challenging the other side's expert
Objections to an expert's qualifications or method are often raised by written motion before trial, with a deadline of their own. In the United States you will hear the names Daubert and Frye for the tests involved, and which one applies depends on the court. If you are representing yourself, ask the self-help center how and when such a challenge is made there.
Direct examination: let the expert teach
Short questions, and answers under a minute
The expert is the one the listener should be hearing, but in pieces. Ask what, how and why, and break in with 'What does that mean?' or 'Why does that matter?' whenever an answer runs long.
Translate every term once
Agree beforehand on the plain word for each technical one and stay with that word all the way through. Two names for one thing sound like two things to someone hearing the subject for the first time.
Put evidence under every assumed fact
An expert may be allowed to give an opinion on facts they were asked to assume, but the opinion is worth only what those facts are. Before the hearing, list each assumption beside the witness or exhibit that supports it, and deal with any that has nothing beside it.
Raise the weak points yourself
The fee, the lopsided case list, the record that does not fit: each sounds smaller in the expert's own words on direct than as a discovery on cross. Give each one a single question and move on.
Save something for redirect
Cross will hold the expert to yes and no. Note each answer that needed a second sentence and, when you stand back up, ask for the rest of it and nothing else.
Cross-examining the other side's expert
Do not argue the science
The witness knows the subject better than you do and has probably been cross-examined before. Stay on ground you can prove from paper: what was reviewed, what was assumed, who is paying, what was said earlier.
Choose three points and stop
A short cross that lands three points is remembered. A long one gives the expert an hour to repeat the direct. Pick the three from the deposition transcript, put the strongest last and sit down after it.
Lead, one fact at a time
Each question should be a statement the witness can only agree with, ending in 'correct?'. An open 'why' hands a practiced speaker the floor, so keep those for the deposition.
Sometimes the best cross is very short
If the expert did your case no harm, or you have nothing you can back with a document, a few questions on what the two sides agree about may serve you better than an attack. Asking for the sake of asking lets the witness say it all again.
If you could not take a deposition
In small claims and some family courts there may be no deposition, and sometimes only a written report. Work from the report: mark what it says was reviewed, what it assumes and what it leaves out, and build your three points from those.