Analysts should clearly explain the reasons for their conclusions or elaborate on the meaning of a match, rather than just stating a match exists.
Scientific language can be confusing or intimidating to jurors. Well-prepared attorneys and scientists who are effective communicators can help bridge the gaps between scientific information and the triers of fact.
Long before a case gets to court, jurists and analysts have an ethical obligation to perform due diligence in evaluating evidence – which includes a commitment to being thorough. They’re also expected to work with an eye on the calendar, giving opposing counsel time for effective preparation.
In addition, defense counsel is ethically bound to properly investigate the evidence, not only to represent the client’s best interests, but to also evaluate the completeness and veracity of evidence to be presented at trial. What do the reports say? Is the meaning clear? Is there language contained within the report that could – or should – be called into question? Are there procedures or conclusions that require further investigation?
The questions that need to be asked become clearer with the deepening of the lawyer’s understanding of forensic science.
Because juries place such trust in the opinions of experts, both legal professionals and forensic experts need to use clear language that explains the limitations of the conclusions and the statistical significance of the results, if applicable.
Therefore, it is incumbent upon attorneys to understand the limitations of the analysis and of the interpretation of the evidence.
Some types of forensic evidence do not lend themselves to the use of statistics. In those cases, it is important to point out to a judge or jury that the evidence cannot be evaluated with statistics, and for them to take that fact into account when weighing the value of that evidence.
When the evidence presented does, however, lend itself to statistical analysis, then it is important to make sure the right language is used so that the jury or judge understands the significance of any results presented.
For example, a hair found at the scene may be called “consistent with the hair of the defendant”. That statement carries a tremendous deal of weight with a jury. But if on cross examination the defense counsel asks the expert to qualify that statement by giving an idea of how many individuals in a population would have hair consistent with the sample, the judge and jury will have a better context in which to qualify the expert’s opinion.
It is also important for an attorney to understand when a forensic methodology that’s amenable to statistical analysis is not backed up by statistics, and to question that missing information.