It has previously been reported (Imhof et al. 1977) that near the midnight trapping boundary the onset of isotropy for electrons and protons often occurs at a sharply defined energy threshold which decreases rapidly with increasing L value. In this paper the addition of energy spectrum measurements to the pitch angle distributions provides new information on the magnetic field configuration in the tail region during these cases. The energy dependent characteristics presented here include the positions and total latitude widths of the transition region from locally trapped to precipitating pitch angle distributions, the intensities and locations of near-coincident enhancements in the trapped fluxes, and the intensities of electron precipitation at energies below the threshold for isotropy. During geomagnetically disturbed times, isotropy at a given energy tends to occur on lower L shells than it does at quiet time, but the widths of the transition region from locally trapped to isotropic pitch angle distributions show no well-defined dependence upon geomagnetic activity. No evidence is found that unusually broad transition regions occur at any one characteristic phase of a substorm. At energie below the isotropy threshold the ratios of precipitating to trapped electron fluxes display large variations ranging from less than 10-3 to more than 10-1. Near the trapping boundary, enhancements are often observed in the fluxes of locally trapped electrons having minimum drift altitudes of ~400km or less. The L shells at which the maximum fluxes occur often display a rigidity dependence which is similar to that associated with the isotropy phenomenon.