It is a critical thing to understand in every lawsuit. Many people just flat do not remember what happened. Ed Marty, the general counsel for the Court of Criminal Appeals, in the end, simply admitted that he did not remember what he told Judge Johnson. This from a trained lawyer with many years experience.
In one of my law school classes, a professor told a story about something another professor did once to illustrate this point. The professor had someone come by right at the start of class and pretend to shoot the professor. The professor falls to the floor and then quickly rises and reassures everyone he is ok. He then asks the class to describe the shooter. Everyone in the class had a different description. Everyone. Trials and lawsuits are not like on TV. Everyone may had a different recollection about what happened. The truth may be very elusive.