The effects of random internal strains on the paraelectric resonance spectra for off-center Li in KCl are investigated quantitatively. Diagrams giving the theoretical line positions and relative intensities are presented for the principal orientations 〈100〉, 〈110〉, and 〈111〉. Where the model for an ideal host crystal predicts only one line, up to six lines are obtained in the present calculation. A direct comparison with the published experimental spectra, taken at 9, 24, 29, 35, 63 and 74 GHz is performed. Very good agreement is found and the magnitude of internal strain has been inferred, yielding values between 18 and 42 bar for different samples. Random internal electric fields are found to be of the order 3kV/cm. For the halfwidth of the main signal, the orientation and frequency dependence is examined and explained by the calculations. The possible use of paraelectric Li as a microprobe for internal strains and internal electric fields in KCl is discussed. The electric dipole moment of Li 7 is found to be 5.9±0.3 Debye in agreement with previous determinations. The “cube edge” tunneling model with equidistant zero field levels, separated by 22.2 GHz for Li 7 , is fully confirmed.