New experimental techniques and novel analysis procedures promote the investigation of three-body processes. Photoinduced three-body decay can be studied by technologically advanced, challenging coincidence experiments as well as by established spectroscopic techniques if physically meaningful decay mechanisms and parameters are introduced. Such kinematic analysis procedures, based on the revaluation of fragment kinetic energy distributions, are presented, ranging from synchronous concerted via asynchronous concerted to purely sequential decay mechanisms. A Dalitz plot representation of a three-body decay is proffered, bridging the gap between established methods and novel coincidence techniques. Results for structurally similar molecules are presented: phosgene, carbonyl chloride fluoride, and thionyl chloride. Competing mechanisms govern the decay of phosgene via the X(1)A(1) ground state and the A(1)A(2) excited state potential energy surfaces. Carbonyl chloride fluoride behaves similarly, but the larger stability of the COF intermediate reduces the complexity brought about by decay channel competition and essentially confirms the phosgene results. Two electronic excited states determine the dynamics of the thionyl chloride decay leading to a competition between three- and two-body decay. Fragmentation from the second absorption,band leads to results comparable to the phosgene decay via the A(1)A(2) state.