Contrary to popular belief, a plaintiff does not necessarily have to take the witness stand at trial in order to sustain his or her burden of proof in a negligence case; some examples of where that doctrine is applied include cases where the plaintiff was either severely injured in a manner that damaged his memory - or killed. In those cases, the court may hold a plaintiff to a lesser evidentiary standard - and even shift the burden of proof to the defendant.
The seminal case on this issue is the 1948 case of Noseworthy v. City of New York, 298 N.Y. 76, 80 N.E.2d 744 (1948). In that case, the plaintiff-decedent was killed by a subway car belonging to the City of New York, and was therefore (obviously) unable to testify as to why he was on the subway tracks before the incident; to the contrary, this information was solely in the defendants' possession.

This rule has been specifically extended to cases involving amnesia. For example, in Sala v. Spallone, 38 A.D.2d 860 (2d Dept. 1972), one of New York's appellate courts stated as follows:

"The trial court committed reversible error in denying plaintiff's request to charge the jury that he should be held to a lesser burden of proof if the jury is satisfied, from the medical and other evidence presented, that he suffers from a loss of memory that makes it impossible for him to recall events at or about the time of the accident and that the injuries he received as a result of the accident were a substantial factor in causing his memory loss."

To be clear, however, before a plaintiff may avail him or herself of the "Noseworthy charge," it must be shown by clear and convincing evidence that the plaintiff's loss of memory makes it impossible for the plaintiff to recall the events of the incident.

This is not - by any means - an easy burden.