  In 2D systems with a spin-orbit interaction, magnetic focussing can be used
to create a spatial separation of particles with different spin. Here we
measure hole magnetic focussing for two different magnitudes of the Rashba
spin-orbit interaction. We find that when the Rashba spin-orbit magnitude is
large there is significant attenuation of one of the focussing peaks, which is
conventionally associated with a change in the spin polarisation. We instead
show that in hole systems with a $k^3$ spin-orbit interaction, this peak
suppression is due to a change in the scattering of one spin state, not a
change in spin polarisation. We also show that the change in scattering length
extracted from magnetic focussing is consistent with results obtained from
measurements of Shubnikov-de Haas oscillations. This result suggests that
scattering must be considered when relating focussing peak amplitude to spin
polarisation in hole systems
