said.“ If you don’ t run deadlines by the expert upfront— vacations, trial windows, report due dates— you can end up under the gun without realizing it.”
When Preparation Breaks Down
Even a well-qualified expert can become a problem if preparation is vague.
One of the earliest warning signs is an expert report that’ s far longer, or broader, than expected.
“ That’ s usually when attorneys realize the expert is covering aspects of the case they never intended,” Guo explained.
Grubbs-Donovan sees this as a shared responsibility, but one that ultimately falls on the attorney.
“ It’ s about setting extremely clear expectations,” she said.“ Look at this event. Comment on this issue. Otherwise, an expert can go on and on without understanding the implications of what they’ re saying.”
That lack of specificity doesn’ t just affect testimony. It can lead to billing disputes when experts review far more records than the attorney intended— another downstream consequence of unclear direction.
How Expert Performance Can Undermine Case Theory
Some expert mistakes don’ t emerge until deposition or trial, when testimony is stress-tested.
Grubbs-Donovan shared an example that illustrates how quickly credibility can collapse:
“ The entire case hinged on the idea that a defendant physician failed to review prior medical records. Then, on the stand, the defense asked the expert whether he had reviewed those records— and he hadn’ t.” The damage was immediate.“ How can you hold the defendant to a standard your own expert didn’ t meet?” she said.“ That single moment blew up the case theory.”
This kind of failure isn’ t about credentials. It’ s about preparation, consistency, and anticipating how testimony will be challenged.
Timing Mistakes That Are Hard To Fix
Bringing an expert in too late remains one of the most common and costly errors.
Late retention compresses vetting, limits preparation, and increases the risk of conflicts surfacing close to trial.
“ We’ ve seen cases where an expert is brought in at the last minute, focuses on a narrow set of records, and only later realizes there are conflicts or missing materials,” Guo said.“ At that point, there’ s just no time to fix it.”
Rebuttal experts are especially vulnerable to this dynamic. Attorneys often scramble to retain someone quickly, expect a narrow review, and underestimate how much context is required to credibly oppose the other side.
When Things Go Really Wrong
Some failures are more human than technical. Guo recalled a case where an expert showed up to a highprofile deposition wearing sandals.“ There was media attention,” she said.“ Of all the trials to do that, it was not the right one.”
In another case, an expert disclosed— just weeks before trial— that the defendant physician had been trained by the expert’ s mentor, creating a conflict the expert was no longer comfortable with.
These are extreme examples, but they share a theme: issues that could have been addressed earlier had expectations, conflicts, and preparation been discussed more thoroughly.
When Replacement Is the Only Option
Replacing an expert is expensive, disruptive, and sometimes unavoidable.
“ It happens most often when the expert can’ t meet deadlines or becomes unresponsive,” Guo said.“ And when you replace an expert, you’ re paying for someone to start from scratch.”
Grubbs-Donovan sees replacement decisions driven by dissatisfaction with reports or unexpected lack of support for the case theory— often late in the process, when options are limited.
At that stage, attorneys may feel pressure to find someone who fits a predetermined opinion rather than reassessing the underlying strategy.
Salvaging A Weak Expert Without Making It Worse
When replacement isn’ t realistic, preparation becomes the only lever left.
“ It comes down to very controlled prep,” Grubbs-Donovan said.“ This is what you comment on. This is how you respond to these questions. Don’ t stray.”
She also noted that presentation matters as much as substance.
“ Attorneys worry about whether an expert comes across as genuine and believable. Sometimes the issue isn’ t the opinion— it’ s demeanor.”
What attorneys shouldn’ t do is react emotionally or adversarially when concerns arise.
The Takeaway Strong cases survive expert challenges when attorneys treat expert selection as risk management, preparation as strategy, and credibility as something that must be actively protected, not assumed.
Or, as Guo put it more simply: if no one raises the hard questions early, they tend to surface at the worst possible moment.
44 The Trial Lawyer