Subtle features of C-13 NMR spectra of perdeuterated methyl groupings are discussed in detail in this work. Standard time-dependent second-order perturbation theory (WBR or Wangsness-Bloch-Redfield theory), couched in a Liouville space formalism, provides the theoretical framework for this development. It is revealed that the C-13 line shape is dependent upon both the scalar coupling between magnetically equivalent deuterons and deuteron autocorrelated and cross-correlated quadrupolar spectral densities. As an experimental demonstration of the presented theory, iterative line shape analyses are applied to standard C-13 spectra and Carr-Purcell spin-echo spectra for the C-13 labeled perdeuterated methyl group in DL-alanine. An activation energy for methyl rotation is determined to be 21.9 +/- 1.2 kJ/mol.