What is the test for "contemporaneous observation" in the context of negligent infliction of emotional distress?

In the years following Dillon v. Legg (1968) 68 Cal.2d 728, 69 Cal.Rptr. 72, 441 P.2d 912, the law surrounding liability for negligent infliction of emotional distress has cast about on a case-by-case basis attempting to define its limits. Analysis, however, reveals we have created a body of law that has no clear consistency or guidelines. Most of the difficulty has rested with attempting to define what is meant by "contemporaneous observation" of the event causing the injury. At this writing, the gamut runs from requiring direct sensory observation, to arriving at the scene in time to mentally "reconstruct" the event. The former is too strict a construction. The latter standard is impossible to apply.