Criminal cases involving road accidents are among the most complex evidentiary proceedings conducted before common courts. Unlike many other categories of cases, determining the course of a road accident often requires reconstructing a dynamic situation, lasting only a few seconds, while simultaneously considering a range of technical, physical, and road user behavior factors. In practice, it is extremely common to lack direct witnesses, surveillance footage, or other objective sources of evidence that would allow for a definitive determination of the course of the accident. In such situations, expert evidence from road accident reconstruction experts becomes crucial.
The importance of expert opinions in road accident cases
It is the expert's responsibility to determine the mechanism of the accident, the vehicle's speed, the possibility of avoiding the accident, the participants' trajectory, the driver's reaction time, and visibility conditions. In practice, the reconstruction report often becomes the central evidence for the entire proceedings. However, this does not mean that the expert's findings override other evidence or that the court can unthinkingly accept the experts' conclusions as final and indisputable.
When special knowledge is required to determine circumstances of significant importance to the case, the procedural authorities are obligated to obtain expert evidence. It should also be emphasized that an expert opinion – like any other evidence – is subject to evaluation by the procedural authority and the parties to the proceedings pursuant to Article 7 of the Code of Criminal Procedure. This evaluation is discretionary, meaning that an expert opinion does not, by law, have any special, superior evidentiary value. Opinions issued by a single expert, a team of experts, or a scientific or specialized institution are equally evaluated.
The principle of free evaluation of evidence and expert opinion
In procedural practice, problems arise when expert opinions begin to replace the court's actual assessment of the evidence. According to established doctrine, particular caution is necessary when assessing expert opinions, especially when other direct evidence is lacking and factual findings are largely based on expert conclusions.
The doctrine emphasizes that uncritically accepting the conclusions of an expert's opinion is unacceptable, as this would violate the principle of free evaluation of evidence and effectively transfer responsibility for resolving the case to a third party. It also notes that excessive reliance on the expert's findings can lead to a situation in which the expert, rather than the court, actually decides the outcome of the decision, which remains unacceptable under the fundamental principles of criminal procedure.
Can a court uncritically accept an expert's opinion?
In road accident cases, it is extremely common for courts to deem expert opinions complete, reliable, and fully credible, accepting their conclusions as sufficient to determine both the course of events and the defendant's liability. However, an analysis of many judgment justifications leads to the conclusion that courts often limit themselves to merely repeating the findings contained in the opinions, without conducting a thorough analysis of the experts' methodology, the quality of the evidence, or the limitations resulting from evidentiary gaps.
This type of practice leads to a situation in which the resolution of the case is de facto entrusted to an expert, and not to the court, which is the only body authorized to make factual and legal findings.
Practical problems of reconstructive opinions
This is particularly important in cases where the evidence is incomplete. Lack of surveillance, direct witnesses, improperly conducted scene examination, or failure to secure key evidence result in reconstruction opinions that are inherently reconstructive and probabilistic.
In such cases, experts rely not only on physical evidence but also on theoretical models, statistical data, professional experience, and assumptions regarding the behavior of road users. Even a small change in input parameters—such as vehicle speed, driver reaction time, pedestrian position, or scene lighting—can result in a completely different reconstruction outcome.
When can an expert opinion be considered incomplete?
This is why a reconstructive opinion requires particularly thorough and critical evaluation. The court cannot limit itself to merely declaring the opinion "clear" or "complete." The judicial body is responsible for truly reviewing this evidence, including analyzing the adopted methodology, the logical reasoning, and the opinion's consistency with principles of life experience.
The procedural body is obligated not only to review expert evidence but also to clarify any existing doubts and address the parties' objections. This is confirmed by the case law of both the Supreme Court and the courts of appeal.
The case law consistently holds that an expert opinion is incomplete, in particular when:
- accepts any data not resulting from the evidentiary material,
- ignores the important circumstances of the case,
- does not take into account all possible variants of the course of the accident,
- eliminates alternative versions of an event without analyzing them.
The Supreme Court has repeatedly emphasized that in road accident cases, a reconstruction opinion should cover all possible variants of the course of the event resulting from the entire evidence.
The limits of an expert's competence
In practice, experts sometimes eliminate a particular version of an event as "unbelievable" during the preparation of their expert opinions, instead of presenting it as one of the possible scenarios requiring court review. Such an approach should be viewed critically.
The expert's role is not to assess the credibility of the participants in the proceedings or to determine the driver's guilt. Their sole responsibility is to conduct a technical analysis of the incident, taking into account all logical and possible versions of how the accident unfolded.
The importance of properly securing evidence
The quality of the evidence secured is crucial to the value of an expert's opinion. Errors made during the scene examination may result in the inability to reliably reconstruct the course of the accident.
Failure to secure trace evidence, determine the location of fragments, conduct lighting measurements, or interview all witnesses creates evidentiary gaps that experts then fill using theoretical assumptions and statistical models. Consequently, final findings may be based more on probability than on reliable evidence.
The principle of in dubio pro reo in road accident cases
In this context, the principle of in dubio pro reo is of particular importance, according to which any unresolvable doubts should be resolved in favour of the accused.
If the course of events cannot be determined with certainty and the expert's opinion is based in part on hypothetical assumptions, the court should not accept the most incriminating version of the accused solely because it was presented by the experts. Criminal liability cannot be based on conjecture, statistics, or the most probable scenario. Guilt in a criminal trial must be proven with certainty, not merely with probability.
Summary
In road accident cases, expert testimony remains crucial evidence, yet requires special care in its evaluation. The professionalism of experts, the quality of the evidentiary process, and the court's critical analysis are fundamental to reaching a fair verdict.
Uncritical acceptance of expert findings leads to a violation of the basic principles of criminal procedure and creates a real risk of issuing a verdict based not on certain factual findings, but on a hypothetical model of the event constructed by a third party.
This article is for informational purposes only and does not constitute legal advice
Legal status as of May 13, 2026.
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