Newsletters Criminal Regulatory 24th Oct 2017

Cross-examining expert witnesses; A Masterclass


  1. A title like this (not my suggestion, I hasten to add) makes me just a little nervous, because having set the bar high, you can almost guarantee this will be anything but a masterclass.
  2. It’s a little like that puffed-up barrister who’s giving it large to the client and his instructing solicitor before the cross-examination of the expert begins. About how he’s going to give the expert a beasting; the witness will regret even having been born let alone having become involved in your case etc. And, as the posturing continues, you can see exactly what’s going to happen. It’s the witness who’s going to wipe the floor with the barrister. And it’s the over-confident advocate, who ought to have spent rather more time on his preparation than on his boasting.
  3. I’ll come back to the dangers of over-confidence, the importance of good preparation in a moment. But before I come to cross-examination just a word or two about experts.
  4. First there are few areas of the criminal law where the expert has a more important role than in a H& S prosecution.
  5. From the prosecution’s perspective (as though of us who defend know to our cost) a well-informed expert, with good practical knowledge and experience of the subject matter; who is balanced in terms of approach; and who is prepared to give ground where appropriate can be a very effective if not a devastating witness. Difficult to break-down and/or to discredit – with the inevitable impact upon outcome for the client.
  6. For the defence, a carefully chosen expert witness can become the most important defence witness, indeed very often the only witness the defendant (particularly if a corporate) dares to call.
  7. Equally if it’s a plea on an agreed basis a good defence expert report can be a very effective tool for submissions on culpability and likelihood of harm and the like. Those dreaded determiners in the Guideline.

Choice of experts

  1. Bearing in mind that much of the preparation for a good cross-examination of the expert witness (ordinarily one of the HSE specialists) depends, good case strategy but also upon the input from your own expert and his/her assistance selecting the areas of the opponent’s evidence to focus upon.
  2. Just a few thoughts of the sorts of things, from the advocates viewpoint, to look for. Most of these are obvious and it’s not by any means exhaustive.
  • Real life experience of, and expertise in, the subject matter of the case.

We often take the question of whether a witness is appropriately qualified as a given, although it is always worth checking. But real-life experience is important. A claim to have general H&S experience will not often help you very much. Nor will an expert who’s forced to concede they’ve had no actual field experience.

  • It’s essential to run what checks you can on credibility … its well-worth putting the expert’s name through the various legal search engines, just to see whether they have been the subject of criticism etc.
  • An ability to communicate effectively and at a level a jury will understand

It’s not just in writing, although a clear and coherent expression of the opinion is essential. It’s also the ability to communicate that view effectively to a jury that is important. In language, all can understand and without condescension.

  • The ability to work hard and to keep to deadlines (or nearly)

As we all know from bitter experience its takes time to get a report into shape and its very much (well it ought to be) a team effort.

  • To be good at joint experts’ meetings.

I don’t know what your experiences are but in a recent case corporate manslaughter case I was involved in with Keoghs, our quite brilliant expert achieved remarkable things at the joint meeting. He had taken the time to prepare an extremely impressive agenda which was in effect a template for the joint statement. He was then skilful enough to take one of the prosecution’s expert into areas covered by another expert and he created a difference of opinion on the prosecution side. Because he was also prepared to take up the task of the drafting the joint statement it ended up in the order he wanted it and containing more by way of concessions than his opposite number had probably intended to give up.

  • Somebody who understands the courtroom and forensic technique

Who knows when to give ground and to make concessions; who is courteous yet firm; who doesn’t become cross and overly-defensive when challenged or taken to task; who knows when to express or to attempt to a view on the ultimate issue and when to hold back

Relevant law

  1. This does sound rather condescending, but make sure you are familiar with the relevant law about the admissibility of expert opinion evidence. Far better to knock the very effective prosecution expert witness out by way of a successful challenge to the admissibility of the evidence, than to have to try to discredit in cross-examination, the witness having delivered all the damage in chief.
  2. Amongst the questions you will want to ask are, is the area which the witness proposes to opine upon, evidence which must be subject of expert evidence? Do the jury need the assistance of the expert on the issue he/she proposes to speak to? Does the subject call for expertise, or can jurors be expected to possess a degree of understanding of the issue such that they can reach informed decisions unaided?
  3. There’s a tendency these days, particularly in s.2/s.3 fatality cases and CM cases, for the regulator to call evidence about the adequacy of systems of work, failings in CDM arrangements etc. which in fact ought not to be the subject of expert evidence at all. Juries are perfectly capable, having been taken to the relevant regulations of reaching its own opinion without needing the assistance of the witness. Juries certainly don’t need help on the ultimate issue.
  4. Check for competence.
  5. Does the subject matter of the opinion form part of a recognisable body of knowledge or experience which is sufficiently organised and recognised to be accepted as a reliable body of knowledge or experience.
  6. Has the expert complied with the CPR (Part 19) and the most recent amendments to it?



  1. As with every other aspect of the criminal trial there is neither escape from, nor any substitution for preparation. No talk on the subject of the cross-examination of an expert can be complete without the necessary preparation
  2. You will have made time (and proper time) with your own expert. Its he/she who is going to provide you will the ammunition and the material with which to cross-examine. You’ll need to make sure your own expert has seen all the relevant material.
  3. Look at the prosecution expert’s working notes, files etc. just occasionally there’s a nugget. Perhaps some rather unwise exchanges between the witness and the regulator in correspondence and in the course of instruction.
  4. You need to know your case and worked out how you intend to establish it. A sound strategy, is, as ever, essential. Where do you hope to end up and on the way, what do you have to confront and deal with on the way? You should be prepared to regularly review the cross-examination note.
  5. Don’t forget what the purpose of cross-examination is. It’s to meet or challenge the essential points made by the expert and, in so far as its necessary with the witness, to put your case.
  6. Too many barristers forget that less is sometimes more. If you’ve got good points which you do not need to explore with the witness, then bank them. If you raise or put these sorts of things, things can only get worse. Remember if the expert has based an opinion on evidence which you’re confident will fall away or disappear, then leave that to happen.
  7. And don’t forget, the cross-examination of the expert is only part of the trial. You have a closing speech and, most importantly, as the defence you go last. So, everything should be building to that moment. To a speech, where you have the last word and unless you make a real mess of it, your opponent will have no chance to contradict.
  8. Narrow down the areas of contentious matters – get through the cross-examination as quickly as it is possible.
  9. Never let it appear that you have not got a grip on your case. If you are prepared you will not.
  10. Have a think about when it would be most convenient for the prosecution expert to give evidence. Conventionally it’s at the end, but is there an argument for seeking to call the expert earlier which might be of advantage to you? What about the defence expert – do you want your witness to follow straight on, ‘back-to-back’, which is in vogue at the moment. There are both advantages and disadvantages to that course.

Manner in which you cross-examine

  1. The cross-examination of the prosecution expert may be your first real exposure to the jury. So, use it to show you and the case you are defending in the most favourable light.
  2. The manner in which you cross examine it of great importance. It will determine the level of confidence the jury have in you and your case. If they lose confidence in you during a big cross-examination, it is difficult to recover and the jury may lose confidence in your case. Remember, there is no second chance to make a first impression.
  3. Show the jury (without showing off) that you know your case and that you are in charge of it. But don’t be patronising or condescending.
  4. Never give the jury the impression that the case you are defending is beneath your dignity, is of little interest to you or, worse still, is not something you don’t believe in. If you appear uninterested in the case then why should the jury care about it or want to reach the right verdict? Every single case is important and every single case can be made to sound interesting if for no other reason that a decision about alleged criminal offending falls to be made.
  5. You must convey the impression of fairness and of having good judgment. Make concessions when its sensible to do so. Defence counsel must earn and retain the trust of the jury.
  6. Don’t go too fast, not everybody will see the points straightaway and make sure there is a good structure, with related points flowing on from each other.

Method/how to cross-examine

37. What should you be seeking to achieve or seeking to avoid during the cross-examination:

  • Keep your composure at all times. Remain calm and do not lose your temper however rude and provocative the witness may become. Do not become rude yourself or bully the defendant. Being firm and robust is different.
  • Control over the witness. It’s essential it is you and not he/she who is in charge and dictating the content and pace. Don’t find yourself answering the defendant’s questions, don’t allow the expert to make speeches – a well-known diversionary tactic to the witness who’s under pressure. Politely, keep the witness honest. If he/she will not answer the question be prepared, politely to take them back to it. If having been given two chances to answer the question, then leave it and move on. If the witness is avoiding the point that’s as good as a concession. So, make that point in your closing submissions
  • Keep your questioning short and to the point. Avoid making speeches at this stage.
  • Take advantage of presentation materials and be imaginative about them. Documents, diagrams, schedules keep the jury engaged and if you can make defence points in documents the jury will keep for the rest of the case, all well and good.
  • Have a good beginning and a good ending. You should be seeking both to start and end on a winning note. Maintain a good order in the middle
  • Always tread carefully and never under-estimate an expert witness. A good expert carries considerable weight in any jury’s eyes. Much better to have agreed to disagree, to have gained a little but not as much ground as you hoped, then to lose out altogether.

Cross examination topics

38. Apart from the substance of the evidence and the dispute between the parties what other lines of cross-examination are open to you?

  • What’s the experts experience of having given evidence previously. Find out before you start – you’d be surprised how inexperienced some experts can be?
  • Have they given evidence for both sides?
  • Have they previously been subject of criticism by a court?
  • Is the witness familiar with the relevant guidance on acting as a witness? With the CPR etc. Have they read the CPS “Guidance Booklet for Experts” or the relevant guidance provided by the regulator?
  • Does the witness have an real life experience of the subject-matter?
  • Has the witness over-extended him/herself and strayed into areas beyond his/her expertise
  • Is there evidence of partiality?

Jonathan Laidlaw QC

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