A model is presented for analyzing positron–electron annihilation spectra obtained using single shot positron annihilation lifetime spectroscopy. The model is tested against data resulting from 1×106 positrons in a single few ns burst impinging on a sample such that the positronium annihilation decay components are accurately reported in a single shot. The model may prove useful in the detection and characterization of nanoscale defects at either the instant of a supplied stimuli or following an extended period of irradiation.