(It differs from "contiguous", or sequential events, and "consequential" or the accumulation of events).
In contemporaneous corroboration the researcher or investigator must put out of his mind any conclusions he may be aware of, so as not to color his judgement. For example, everyone knows the verdict of history as to who won World War II. Now if the investigator begins with the conclusionary premise: "How did this come about?", he is using the "reverse method", seeking out facts to support his conclusion, and perhaps overlooking evidence of enormous consequence. Under the "contemporaneous" method of investigation, the researcher is ignoring conclusions and seeking out the heart and soul of the matter that consequently led to conclusions.
The contemporaneous method seeks to "live the life" of the event, beginning at a point in time and moving forward. The reverse method, also sometimes known as "reexamining a verdict", begins with a conclusion and works backward. Historians call this a backward argument, or "arguing backwards". The danger under the reverse method is beginning with a conclusion, one often arrives at the same result.
Contemporaneous method was demonstrated and popularized several years ago with the PBS television documentary The Civil War, an achievement in that medium for using historical narrative and still photography. Instead of traditional recreations by actors and set designers, the text was carried forward by studied historians speaking in the present tense—narrating events 130 years prior. This may have sounded peculiar to the lay audience yet employed the exact terms, form and method historians use to gain the time depth perception lacking when "looking back at events" using the reverse method.
For years after the TV event, it became fashionable for cop shows, both SWG (Hollywood Screen Writers Guild) productions and Reality shows, to show "real time" investigators recreating events of homicides and discussing sequences using the contemporaneous method—in the present tense—about past events, ignoring any judgement or conclusion already obvious. And the methods' purpose is obvious, to gain a greater understanding of the contemporaneous event leading to the conclusion, not the conclusion itself.