Measurements of the electron spin polarization parameter A have been performed for HBr in the energy region between the two ionization thresholds, (II3/2)-I-2 and (II1/2)-I-2. Using the multichannel quantum defect theory and formulas derived for the spin parameters in intermediate coupling between Hund's cases (a) and (e), calculations for both the cross section and the A parameter have been performed. It is shown that the values of A for each Rydberg resonance change with n, following the change from Hund's case (a) to case (e). In the approximations used in this paper, no simple relation between the sign of A and the value of J(+), the rotational angular momentum of the ion core, was found. Values for the calculated angular asymmetry parameter beta and the spin polarization parameter xi are also presented. Since our calculations reproduced only part of the observed resonances, and since the measurements of the A parameter have been performed in relatively narrow energy regions, one could not perform an extensive comparison between theory and experiment. However, some of the peculiarities of the behavior of the A parameter observed experimentally have been qualitatively reproduced by our calculations.