THE RELIABILTIY OF WITNESS RECOLLECTION
When a collision occurs, the usual starting point for determining the circumstances is witness information. Involved persons may provide an immediate oral or written statement, or may offer their version of events at a later date, such as on discovery. The recollection of witnesses, whether involved in the incident or not, is considered valuable evidence during subsequent settlement negotiations or litigation. How reliable is this information?
Several factors should be considered to assess the reliability of any particular stated fact. These factors fall into two general categories: the first relate to intentional misstatement (lying); the second relate to honest though mistaken recollections.
The reliability issues raised by witness interest in the outcome of litigation are fairly obvious, and the frequency of lying by involved parties is high. However, circumstances of honest though mistaken memories are likely equally common, and these raised significant difficulties in determining the circumstances of a collision: after all, no reason exists to doubt the credibility of the independent witness' statements. Thus, it is important to understand factors that may lead to honest though false memories, and these are discussed below.
Power of Suggestion
Witnesses are very susceptible to the power of suggestion. Asking a witness how "fast" a car was travelling will illicit higher reported speeds than asking how "slowly it was moving.
Witnesses tend to rationalize the post-collision evidence, particularly smashed vehicles. Someone seeing a collision will often hear the impact noise that attracts their attention, and though they will not have seen the vehicles prior to impact, they will 'reconstruct' what they believe occurred. This reconstruction becomes a 'memory'. We have been involved with cases where high speed has been reported by witnesses for a heavily damaged vehicle, even though this is conclusively contradicted by a reconstruction.
Research has shown that it is relatively easy to introduce false memory. Media coverage or written recollections by other witnesses - if reviewed by a witness - could suggest "facts" to the witness. Witnesses will often discuss the occurrence amongst themselves and false memories can result.
A further problem is the subjective element of observations. Ones ability to judge the rate of speed of a vehicle depends on the circumstances during which the observation is made and the vantage point of the observer. A vehicle passing by a pedestrian in close proximity, for example, will tend to generate an impression of higher than actual speed.
A forensic evaluation is typically based on undisputed physical evidence, and is therefore generally more reliable than witness versions of events. Physical evidence can be helpful in determining which witness statements are useful and which are misleading. An experienced investigator can normally sort out which reported information is reliable, and add this to the information available from physical evidence to complete a proper reconstruction of events.
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