We present single-dish 350 μm dust continuum polarimetry as well as HCN and HCO+ J = 4 → 3 rotational emission spectra obtained on NGC 1333 IRAS 4. The polarimetry indicates a uniform field morphology over a 20'' radius from the peak continuum flux of IRAS 4A, in agreement with models of magnetically supported cloud collapse. The field morphology around IRAS 4B appears to be quite distinct, however, with indications of depolarization observed toward the peak flux of this source. Inverse P Cygni profiles are observed in the HCN J = 4 → 3 line spectra toward IRAS 4A, providing a clear indication of infall gas motions. Taken together, the evidence gathered here appears to support the scenario that IRAS 4A is a cloud core in a critical state of support against gravitational collapse.