Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)We investigate optical torques over absorbent negative refractive index spherical scatterers under the influence of linear and circularly polarized TEM00 focused Gaussian beams, in the framework of the generalized Lorenz-Mie theory with the integral localized approximation. The fundamental differences between optical torques due to spin angular momentum transfer in positive and negative refractive index optical trapping are outlined, revealing the effect of the Mie scattering coefficients in one of the most fundamental properties in optical trapping systems. (C) 2011 Optical Society of America2823542363Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)CePOF, Optics and Photonics Research Center [2005/51689-2]Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [2009/54494-9]CePOF, Optics and Photonics Research Center [2005/51689-2]