Circumstances, and people eyewitness testimony: a recollection of the actions, circumstances, and the people involved by witnesses and/or victims of a crime. Crimes involving a single witness or victim, additional material or circumstantial corroborating evidence are often not available. Scientific research on eyewitness testimony draws heavily upon the fields of cognitive psych. (perception, short and long term memory, thinking, decision making) and social psych. (influence of social variables upon human behaviour i. e, conformity, self-presentation, attitudes) Variables related to eyewitness testimony: the effects of witness age, time delay between observation and report, repeated and suggestive questioning procedures, mental rehearsal, and identification decisions. A useful distinction frequently made by researchers in the area of eyewitness testimony is that between system and estimator variables. Basics of memory and its implications for eyewitness testimony. Most judicial systems have developed rules of evidence, whereby the admissibility of evidence is assessed based in part on its reliability.