General discussion framework and overview

Eye witness testimony can be unreliable for a plethora of reasons, not the least of which include ulterior motives on the part of the individual testifying. People do not always testify to ensure that justice is served. Witness tampering can definitely affect the veracity of what eye-witnesses state when they testify, including partisanship tendencies towards sides of the issue considered in court.

From a cognitive perspective, however, there have been several studies performed that empirically validate the fact that the mind and various facets of it is not always consistent with reality. Perhaps the most tenuous aspect of cognition in regards to eye-witness testimony relates to the nature of memory. People do not always remember things correctly. Crucial details including those related to size, color, and even sequence, are extremely mutable to one's memory. Eye-witnesses, then, can actually observe an event that they are brought into court to testify about, witness or hear it correctly due to accurate sensory processing, and still not correctly recall it with the proper details on the witness stand.

It is worth noting that such occurrences can take place even when witnesses are willing to cooperate on the side of law and justice and recollect some relevant facets of a case as accurately as possible. There are a number of explanations pertaining to the cognitive process for why memory can vary according to individuals and not necessarily according to the events that they are striving to recollect. Memory is affected by several factors, one of the most eminent of which is time. In general, people tend to recollect the details of short-term memory better than those associated with long-term ones, although it is also possible for the short-term memory of individuals (due to age or perhaps substance abuse) to rapidly deteriorate as well.

Additionally, there are inherent links between emotions, cognition, and motivation that can substantially impact one's memory. Factors such as how a person was feeling at the time that they witnessed an event can definitely affect their memory of that event. For instance, if someone were really angry or elated at the time that an event in question took place, such feelings impact how they not only perceive an event, but also how they remember it. This point pertains to another about the unreliability of eye-witness testimony -- not everyone is able to perceive things the same way or at a level of complete proficiency. There are biases that can affect the cognitive process that relate to sensory ones which determine how things are perceived. Depending on a host of factors that are affecting a person at a particular time, he or she may be more receptive to certain sensory data (such as the lyrics to a song) than to gauging the distance of the driver in front of him or her. This fact is alluded to in experiments in which a group of individuals offer varying accounts of a single event.