A forensic expert I know has a simple rule: he works for the evidence, not the client.
It sounds clean. And it’s absolutely right as far as it goes. The opinions have to follow the evidence, full stop. Your findings don’t change because of who’s paying the bill.
But here’s the part that rule doesn’t cover: the strategic context you’re working in is different depending on which side retained you, and being aware of that context makes you a better expert — not a biased one.
On the plaintiff side, you’re typically introducing evidence and supporting a narrative. On the defense side, you’re often critiquing the plaintiff’s evidence and introducing doubt. The cross-examination you’ll face differs. The questions retaining counsel will ask on direct differ. The standard of persuasion you’re working within differs.
None of that changes your opinions. But all of it should change how you prepare.
The Objectivity Requirement
Let’s start with the non-negotiable.
Expert witnesses have an obligation to the court that supersedes their obligation to the retaining party. FRE 702 and the broader professional standards of digital forensics require that your opinions reflect your genuine assessment of the evidence — not an assessment shaped by who you want to win.
This is not merely an ethical nicety. It’s practical. Your credibility as an expert is your most valuable professional asset. An expert who is seen as an advocate rather than an analyst will be impeached effectively on cross-examination, and that impeachment damages not just the current case but every subsequent case you work.
The test I use: could I have reached the same opinions if I had been retained by the other side? If the honest answer is no — if my opinions have been shaped by who retained me — I have a problem. If the answer is yes, I’m doing my job.
This doesn’t mean you go looking for ways to hurt your client’s case. You analyze the evidence within your assigned scope, form your honest opinions, and let retaining counsel decide how to use them. If your findings don’t help their case, a good attorney will either work with what they have or find a different expert. What they won’t do — if they’re operating ethically — is ask you to shade your opinions toward their preferred outcome.
Testifying for the Plaintiff: What to Expect
When you’re the plaintiff’s expert, you are typically the one who examined the primary evidence and is explaining to the jury what it shows.
Direct examination is your opportunity. Retaining counsel shapes the direct examination to build their case narrative. Your job is to explain your methodology, present your findings, and support the opinions in your report — in language a non-technical jury can understand.
The challenge on the plaintiff side is overreach. Plaintiff counsel often wants you to say more than the evidence supports — to draw conclusions that go beyond your forensic findings into territory that sounds more damaging to the defendant. Resist this. Overstating your findings invites effective cross-examination and undermines your credibility on the core points where the evidence is solid.
Cross-examination targets from defense counsel:
- Methodology gaps: Did you consider alternative explanations? Why did you use that tool vs. another?
- Limitations you didn’t acknowledge: What can’t your analysis determine?
- Cherry-picking: Did you examine all the evidence, or just the evidence that supports your conclusions?
- Financial interest: How much are you being paid? What percentage of your work is for plaintiffs?
That last question — what percentage of your work is for plaintiffs — is designed to suggest you’re a “hired gun” for the plaintiff’s side. If 90% of your work is for plaintiffs, that’s a reasonable line of attack. If your plaintiff/defense ratio is more balanced, say so.
The narrative structure on the plaintiff side: Your testimony builds toward a conclusion. “Here’s what I found, here’s what it means, here’s why my interpretation is the most supportable one.” You’re making an affirmative case.
Testifying for the Defense: What to Expect
Defense-side forensic expert work is often fundamentally different in character. You may be critiquing the plaintiff’s expert’s methodology rather than presenting independent findings. You may be introducing alternative explanations for evidence the plaintiff has already presented. You may be identifying what the evidence does not show as much as what it does.
Critique vs. independent analysis. On the defense side, you frequently get retained after the plaintiff’s expert has already produced a report. Your first task is often analyzing that report for methodological problems, unsupported leaps in logic, or overlooked alternative explanations.
This is legitimate and valuable expert work. But it requires care: your critique has to be grounded in actual methodological deficiencies, not advocacy for the defense position. If the plaintiff’s expert’s methodology is sound, say so — and then focus your opinions on the specific areas where you legitimately disagree or where the evidence is genuinely more ambiguous than the plaintiff’s report suggests.
The “hired gun” problem is sharper on the defense side. Defense experts are more likely to face the perception — and the cross-examination question — that they’re paid to say “maybe” about everything. The way to counter this is to be affirmative where you can be. Don’t just critique; offer your own best assessment of what the evidence shows and doesn’t show.
Direct examination on the defense side: Defense counsel’s direct examination of you often comes after the plaintiff’s expert has testified. You’re in a rebuttal or alternative-narrative position. Structure your testimony to clearly explain: where you agree with the plaintiff’s expert, where you disagree and why, and what alternative conclusions the evidence supports.
Cross-examination targets from plaintiff’s counsel:
- What would change your opinion? Pushing you toward “nothing would change your opinion” (which sounds biased) or toward “the following evidence would change it” (which they’ll argue is absent)
- Why didn’t you do your own independent analysis? (Answer: you did, where you were asked to; you also reviewed the plaintiff’s work)
- Aren’t you just nitpicking the plaintiff’s expert? (Answer: identifying methodological problems in an opposing expert’s analysis is exactly what a defense expert is retained to do; you’d apply the same scrutiny to your own work)
Adjusting Your Communication Style by Side
The substance of your opinions doesn’t change. The communication style — how you structure explanations, what you emphasize, how you handle uncertainty — can legitimately vary.
On the plaintiff side, you’re typically explaining technical findings to establish what happened. Clarity and accessibility matter. You want the jury to understand your analysis well enough to find it compelling, not just true. Use concrete analogies. Move from simple to complex. Establish each foundational point before building on it.
On the defense side, you’re often introducing nuance and uncertainty into what the plaintiff has presented as a clear story. Technical precision matters more here — you need the jury to understand exactly why the plaintiff’s conclusions are overstated or unsupported. You may spend more time on what the evidence cannot tell us and less time on what it can.
Neither approach is advocacy. Both are honest communication about the evidence calibrated to the actual questions before the court.
Maintaining Credibility Through Both Roles
The experts who maintain long-term credibility testify on both sides. Not always in equal proportion — your professional network may naturally deliver more work from one side — but courts and attorneys notice when an expert works exclusively for one side.
Work both sides when appropriate. If you’re known exclusively as a plaintiff’s expert or exclusively as a defense expert, you’re more vulnerable to the hired-gun impeachment. Taking cases from both sides when the evidence supports your opinions is the most credibility-preserving practice.
Hold firm on your opinions. The most effective cross-examination technique is sustained pressure — asking the same question multiple ways until the expert budges. Don’t budge. If your opinion is supported by your analysis, defend it. If new information genuinely should change your opinion, say so and explain why. But don’t change your opinion because a skilled attorney is being aggressive.
Acknowledge common ground with the opposing expert. In your testimony, acknowledge where you and the opposing expert agree. This signals objectivity. It tells the jury you’re not simply contradicting everything the other side says — you’re identifying the specific points where you have a genuine, evidence-based disagreement. Those specific points of disagreement will carry more weight if you’ve established common ground first.
Your testimony record is public. Prior deposition transcripts and trial transcripts are available to opposing counsel. If you’ve said something inconsistent in a prior case, it will be found. Be consistent. Be honest. And be aware that everything you say under oath is part of a permanent record.
FAQ
Is it acceptable to ask retaining counsel what outcome they’re hoping for before I begin my analysis?
Knowing the outcome retaining counsel is hoping for isn’t inherently problematic — they’re going to tell you anyway once they brief you on the case. What matters is that you don’t let their hoped-for outcome shape your analysis. Analyze the evidence objectively, form your opinions, and then present them to counsel. If your opinions help their case, great. If they don’t, that’s also information counsel needs to know.
What if retaining counsel asks me to soften a finding that hurts their case?
This happens. The appropriate response is to explain that you can only testify to what your analysis shows. You can help counsel understand the significance and context of the finding, identify how to address it on direct before opposing counsel raises it on cross, and advise on whether additional analysis might provide more nuance. What you cannot do is misrepresent your findings or omit material information because it’s inconvenient for your client.
Can I testify for plaintiff in one case and defense in a similar case simultaneously?
Yes, as long as the cases aren’t related and you don’t have a conflict of interest. Your opinions in each case follow the evidence in that case. It’s possible — and professionally healthy — to conclude that plaintiff has the better of the evidence in Case A while the defense has the better of it in Case B. That’s not inconsistency; that’s what happens when cases have different facts.
How do I handle it when I think my retaining counsel is asking me to overstate my findings?
Have a direct conversation. Explain that you can support [X conclusion] based on your analysis, but not [Y conclusion] — and explain why. If counsel persists, explain that overstating your findings will hurt the case when opposing counsel challenges it on cross-examination. Good counsel will listen. If counsel continues to pressure you, you need to have a harder conversation about whether you can continue in the engagement.
What percentage of plaintiff vs. defense work is “normal”?
There’s no required ratio. Some highly credible experts work primarily for one side because of their referral network. What matters is that your opinions are consistent with the evidence, that you could defend your methodology in either context, and that you’re not seen as systematically biased toward a predetermined conclusion. If 100% of your cases go to one side, be prepared to address that in cross-examination with an honest explanation.
