We’ve been writing in recent posts about neuroscience evidence in criminal cases, and the court system’s reluctance to accept such evidence because of its perceived lack—perceived or actual—of reliability. Reliability, we noted, is a big issue with any piece of evidence, and one of the tasks of a criminal defense attorney is to ensure that the evidence prosecutors are presenting in support of charges meets minimum standards of reliability.
Reliability refers, of course, to the question of whether evidence is accurate for proving a material fact in a case. Whether the evidence in question is witness testimony, documents, or physical evidence of some sort, evidence must always be scrutinized for its reliability or accuracy. Knowing how to effectively cross-examine witnesses and scrutinize physical or documentary evidence is important to ensure that unreliable evidence doesn’t make an undue impact on a case. Where evidence is particularly unreliable, it is important to make sure it isn’t admitted to trial at all. And when unreliable evidence does make it do court, an experienced attorney will help a jury to consider the evidence in the proper light.
In addition to reliability, a criminal defense attorney will also be concerned with the relevance and potentially prejudicial effect of any evidence presented by prosecutors in a criminal case. Evidence which may be reliable, but which is not relevant to any material issue in a criminal case, is not going to be admissible. Different types of evidence, of course, have to be weighed in terms of their ability to prove a material fact in the case, and just because a piece of evidence is admitted to trial as meeting minimum standards of relevance does not mean it should be given significant weight by the jury.
The prejudicial effect of evidence refers to the fact that some evidence can be both reliable and relevant with respect to a material issue in a case, but still present an undue risk with regard to some aspect of the case, such as confusion of issues, misleading the jury and unfair prejudice.
All of these evidentiary issues are written into both state and federal codes, and an experienced attorney is expected to have a solid grasp of the rules, how to initiate related motions, and how to navigate the whole process while zealously advocating for the interests of a client.
Title VII, Evidence; Chapter 90: Evidence Code
Federal Rules of Evidence