A range of constant pressure dead-end filtration experiments with additional torsion shear are analysed, Two cases are considered: 1) suspensions of neutral particles (i.e. zero zeta potential); and 2) suspensions of double layer interacting particles (high zeta potential). In both cases the data, which have been recorded in the form of outflow volume of the filtrate as a function of time, show an increase in the cake density when shear is applied at the final compression state. In the case of suspensions of neutral particles increasing the shear rate has practically no effect on the filtration rate until the final stage of the filtration process, while suspensions of interacting particles display effects due to shear in the intermediate stage as well. This behaviour is explained in terms of the state of stress in the filter. For neutral particles suspended in an aqueous solution the problem is simplified by modelling the suspension/cake system as two Newtonian fluids of different viscosities. It is argued that this is an acceptable approximation for suspensions that consist of neutral particles. A more elaborate model is needed for suspensions consisting of interacting particles, allowing for a reduction in skeletal stress at higher shear rates. The analytical model put forward identifies fluctuations in field parameters; it is verified by means of a lattice-Boltzmann numerical simulation. Finally, it is shown that the higher cake density established towards the end of the filtration process is due to a nonhomogeneous compaction mechanism, which causes the cake to form vertical structures that are orientated in the direction of the major principal skeletal stress directions. Shearing the cake causes the orientation to change with respect to the apparatus axis, thus weakening the one-dimensional response of the cake material.