In the courtroom, especially in the case of a jury trial, information which is presented to the court is subject to various limitations and controls. For example, in the case involving whether a driver ran through a stop sign in Pennsylvania without stopping it might not be fair for the prosecution to introduce a prior conviction for drag racing in California ten years earlier. The law of evidence places certain limits on the type and quality of information which can be presented in any given case.
I must confess to becoming hooked recently on old episodes of Perry Mason, the famous series which ran on television in the late 1950s. The aggressive and often inept prosecutor, Hamilton Burger, would often object to testimony and evidence offered by Perry Mason as being “incompetent, irrelevant and immaterial”. The fact of the matter is, Mr. Burger was often correct in his objections.
Competent evidence means evidence that is legally admissible to prove the point in question. Direct testimony by a witness as to what he or she saw is competent evidence on the point. Hearsay statements (i.e., statements by a witness as to what another witness said they saw) would not be competent evidence and would not be admissible. In our example, a witness would be allowed to testify that he saw the car run through the stop sign; one would not be allowed to testify that they were told by a third party that the car ran through the stop sign.
Relevance is also a requirement for the admission of evidence. In our example above, a conviction for a different offense ten years earlier in another state would hardly be relevant to whether the driver in our example ran through the stop sign in Pennsylvania. The only similarity between the two events is that they involve the same driver and an automobile. The offenses are different, they are separated in time, and essentially bear no relation to one another.
For evidence to be material, it must have a logical connection to a fact or circumstance affecting the outcome of the case. In our example, it might be material that the driver admitted at the scene that he was late for work, which might explain why he ran the stop sign. It would not be material if a witness stated that he heard loud music coming from the car (it has nothing to do with whether or not the vehicle stopped for the stop sign.)
In the case of a jury trial, the trial judge is especially sensitive to preventing inflammatory but ultimately irrelevant information from being brought before the jury. For example, in a shoplifting case, evidence offered that the defendant was a member of the Communist party would never be allowed because it is both irrelevant to the underlying case and potentially inflammatory to the detriment of the defendant. In some cases, even relevant evidence is prohibited if it is so potentially inflammatory as to cause the jury to overreact to it. This is why gruesome photographs of accident victims are sometimes not allowed to be shown to the jury, for fear that they might overreact in their judgment against the defendant. In the end, it is all about the court’s control over the flow of competent, relevant, material evidence in order to arrive at a just outcome.
– Kevin Palmer