Antimony sulfo-iodide (SbSI) exhibits strongly-coupled photoconductive, semiconducting, and ferroelectric properties. Until the discovery of the lead-oxide ferroelectric relaxor compounds, SbSI was the strongest known piezoelectric. The structure of SbSI is highly anisotropic, consisting of Sb_2S_2I_2 double chains whose orientation defines the long crystal axis. The chains are held together via van der Waals interactions. Below 292K SbSI undergoes a weak first-order structural phase transition from a paraelectric (orthorhombic D^16_2h) state to a (orthorhombic C^9_2v) ferroelectric state. The compound sublimes above 450 K. We wish to perform neutron scattering measurements on MERLIN at 300K and 400K on a two-crystal composite sample with 0.3 meV energy resolution to study the nature of ferroelectric phase transition and the damping and anharmonicity of the TA and low-lying TO modes.