Photoelectron-photofragment coincidence spectroscopy is employed to study the dissociative photodetachment (DPD) dynamics of S2O2- at 258 nm. Experimental data and theoretical calculations show evidence for photodetachment from a trigonal form of S2O2-. The vertical detachment energy of this isomer was determined to be 3.73 +/- 0.02 eV. An upper bound of 2.41 +/- 0.14 eV is determined for the enthalpy of the reaction S2O2- --> S + SO2 + e(-) at 0 K. The observed dynamics are interpreted in terms of dissociative photodetachment of S2O2-to S(P-3) + SO2((1)A(1)) + e(-), S(D-1) + SO2((1)A(1)) + e(-), and S-2((3)Sigmag(-)) + O-2((3)Sigmag(-)) + e(-) product channels. The S-atom channels are characterized by a large photofragment kinetic energy release and an anisotropic photofragment angular distribution peaked along the electric vector of the laser. The S-2 channel has a low kinetic energy release consistent with elimination of highly vibrationally excited O-2 from a strained form of the trigonal isomer.